Which salivary gland secretes amylase

In contrast, the acinar system of the SMG of rodents, unlike that of humans, contains a single type of seromucous acinar cells, and this produces both mucin glycoproteins, which is a characteristics of mucous cells, and various bioactive proteins as well as water and ions, which is a characteristics of serous cells.

Furthermore, the duct system of the rodent SMG differs from that of the human SMG, in that a special duct portion called the granular duct or granular convoluted tubule GCT exists between the intercalated duct ID and striated duct SD [ 10 ]. During the postnatal growth of rodents, especially of mice, extensive development of the GCT from the SD takes place preferentially in males during puberty, resulting in a marked sexual difference in the morphology and function of the duct system in adults [ 2 , 3 ].

The epithelial cells of the GCT have abundant secretory granules that contain various bioactive peptides such as nerve growth factor NGF and epidermal growth factor EGF [ 1 , 6 ]. Amylase is a digestive enzyme for polysaccarides that is widely distributed in nature and classified into several types. This enzyme is further divided into two isozymes, i. All subsequent experiments were conducted in accordance with the Guidelines for the Care and Use of Laboratory Animals at Kanazawa University.

Male and female animals under various experimental conditions were sacrificed under pentobarbital anesthesia by transcardial perfusion with physiological saline. Each sample was analyzed in triplicates and samples from 4 or 5 different animals were analyzed to determine each value. ISH was performed as described previously [ 17 ].

After hybridization, tissue sections were washed in 0. ISH results were confirmed in the salivary gland specimens of 3 different animals. After being blocked with 0. The sections were then subjected to observations under an Olympus BX50 microscope. IHC results were confirmed in the salivary gland specimens of 3 different animals. Differences with a P value less than 0. The relative levels in the three salivary glands of male mice were approximately 1, 0.

ID cells also had a signal similar in intensity to that in acinar cells, but ED cells had a markedly weaker signal. Negative control sections treated with the DIG-labeled antisense probe mixed with an excessive amount of the unlabeled antisense or sense probe had no signal at all Fig.

ID cells and SD cells were also weakly positive for the signal. An excess amount of a non-labeled sense probe was added in b for the negative control. Acinar cells A were also weakly positive, whereas excretory duct cells E were almost negative for the signal. No signal was detected in any cells. Most of the epithelial cells, including acinar and striated duct cells S , were weakly positive for the signal.

Serous demilune cells D of acini were moderately positive, whereas mucous acinar cells M were almost negative for the signal. Acinar cells were strongly positive, whereas intercalated duct I and excretory duct E cells were almost negative for the signal.

The molecular weights kDa of the immunoreactive bands are indicated. Reactivity in acinar and ID cells was markedly weaker than that in GCT cells, but was stronger than that in acinar and ID cells of the negative control sections, which were treated with the antibody preabsorbed with the corresponding oligopeptide Fig.

The primary antibody was replaced with non-immune goat serum in b for the negative control. No immunoreactivity was detected in any cells. Acinar cells were weakly positive and striated duct cells S were moderately positive for the immunoreaction. Control of secretion is also dependent on the perception of taste and smell.

The gustatory stimulus is more important than the masticatory stimulus in controlling the salivary secretion. The secretion of saliva occurs by the process of stimulus secretion coupling. This refers to the events involving release of neurotransmitter from vesicles in nerve terminals adjacent to parenchymal cells which stimulate them to discharge secretory granules, water and electrolytes as well as contraction of myoepithelial cells.

Norepinephrine activates both alpha and beta adrenergic receptors, while parasympathetic transmitter like acetylcholine activate cholinergic receptors. Alpha adrenergic receptor stimulation results in protein secretion while beta adrenergic or cholinergic stimulation results in low protein secretion and secretion of water and electrolytes.

Substance P stimulates alpha adrenergic and cholinergic secretion of saliva. The following flow chart Figure 4 shows the events associated with stimulus secretion coupling which involves the basic process of receptor stimulation which results in increase in the concentration of a secondary messenger, which will further trigger additional events leading to a cellular response [ 3 , 4 , 5 , 6 ].

Flowchart depicting sequence of events following neural stimulation. Copious watery saliva is secreted in response to parasympathetic stimulation and thicker saliva in response to sympathetic stimulation. Other factors affecting saliva composition are flow rate, circadian rhythm, duration of stimulus, nature of stimulus and diet. During sleep very little saliva is secreted by major salivary glands and majority of the saliva secreted is by the minor salivary glands.

Concentration of saliva depends on rate of flow and not on nature of stimulus [ 2 , 3 , 4 , 5 , 6 ]. Historically, it was suggested that parotid salivary gland secretes a hormone called parotin which was considered to have a protein-anabolic function and deficiency resulted in diseases such as chondrodystrophia fetalis, Kaschin-Beck disease, etc.

An increase in the flow of saliva is referred to as sialorrhea ptyalism , while a decrease in the salivary flow is referred to as xerostomia dry mouth. Xerostomia is observed in menopause, patients treated by radiation therapy, old age, prolonged use of tranquilizers, amphetamines, antihypertensive and anticonvulsant drugs. A number of systemic conditions affect the functioning of the secretion of salivary glands. Hyperthyroidism, pernicious anemia, vitamin D deficiency, multiple sclerosis and poorly controlled diabetes mellitus affect the salivary glands.

Inflammatory, infective and neoplastic diseases also disrupt the activity of salivary gland secretion. Salivary secretion is influenced by hormones. For example antidiuretic hormone facilitates water reabsorption by striated duct, aldosterone causes increased sodium reabsorption by striated duct, testosterone and thyroxine increase salivary secretion [ 2 , 8 , 9 ]. Protection: the saliva contains mucin and glycoproteins which provides it with lubricating properties and moistening the oral cavity, thus preventing friction between the oral structures during physiological functions like mastication.

The constant flow of saliva provides clearance of accumulated food debris and microorganisms. Mucins also provide thermal and chemical insulation. Proteins, glycoproteins and mucins form a coating called pellicle formation.

Saliva acts as a source of calcium, phosphate, fluoride, statherin and proline rich protein which maintain the integrity of enamel and repair. Digestion: water and mucin content of saliva aids in bolus formation during the process of mastication. Antimicrobial activity: mucins aid in providing a physical barrier to infections by preventing attachment of microorganisms to tooth and tissue surface. Presence of secretory immunoglobulin A provides immune defense.

Peroxidase, lysozyme, lactoferrin, histatin, mucins, agglutinin, defensins and cathelicidin also help in providing antimicrobial activity. Buffering: bicarbonate, phosphate, basic proteins, urea and ammonia help maintain the pH and neutralization of acids. Tissue repair: salivary glands release growth factors, trefoil proteins into saliva which aid is tissue repair and regeneration. Taste: saliva acts as a solvent in which molecules from food items can dissolve and reach the taste buds, epidermal growth factor and carbonic anhydrase VI maintains taste buds.

Role of saliva in periodontal pathology: saliva exerts a major influence on plaque initiation, maturation and metabolism. The first step in plaque formation is formation of pellicle followed by plaque formation and maturation [ 1 , 2 , 3 , 4 , 5 , 6 , 8 , 9 ]. Salivary proteins may play a role in plaque mineralization. It is indicated that esterase, pyrophosphatase, acid phosphatase and lysozyme may be involved.

Persons with heavy calculus, have higher levels of salivary glycoproteins than non-calculus formers [ 1 , 2 , 3 , 4 , 5 , 6 , 8 , 9 ]. Polymorphonuclear neutrophils PMNs reach the oral cavity by migrating through the lining of gingival sulcus. Skougaard and Bay, believe that orogranulocytic migratory rate correlates with severity of gingival inflammation and is therefore reliable index for assessing gingivitis [ 8 , 9 , 10 , 11 ]. The saliva acts as an important diagnostic oral fluid owing to its ease and non-invasive mode of collection.

A number of components secreted in saliva can be assessed and used to assess diseased states. A few of the components used as specific biomarkers for detection of periodontal disease include immunoglobulins Ig such as IgA, IgM, IgG which interfere in adherence and bacterial metabolism and are present in increased concentration in saliva of chronic and aggressive periodontal patients.

Nonspecific markers for aggressive periodontitis include mucins which interfere with the colonization of Aggregatibacter actinomycetemcomitans A.

Markers for chronic periodontitis include lysozyme which regulates biofilm accumulation and peroxidase which interferes with biofilm accumulation. Nonspecific markers for both chronic and aggressive periodontitis include histatin which neutralizes lipopolysaccharide and enzymes known to affect periodontium and C-reactive proteins which are present in increased concentrations in saliva and serum of patients with periodontitis [ 8 ].

Other areas where saliva can be used for diagnosis of diseases and conditions include cystic fibrosis, which is a genetically transmitted disease of children and young adults characterized by generalized exocrinopathy.

In this condition, saliva contains increased calcium levels, elevated levels of sodium and a decrease in flow rate [ 8 , 9 ]. A low resting flow rate and abnormally low stimulated flow rate of whole saliva. An antibody p53 can also be detected in the saliva of patients diagnosed with oral squamous cell carcinoma SCC.

Saliva can be used for monitoring of anti-epileptic drugs as a positive correlation between salivary and serum carbamazepine levels has been observed. In another study, salivary levels of phenobarbital and phenytoin demonstrated excellent correlations with serum levels of these medications.

Other drugs that can be identified in saliva are amphetamines, barbiturates, benzodiazepines, cocaine, phencyclidine PCP , and opioids [ 8 , 9 , 10 ]. Steroid hormones can be detected in saliva. Recent focus on the potential role of periodontal disease as a risk factor for cardiovascular and cerebrovascular diseases [ 13 , 14 ] and the occurrence of pre-term low-birth-weight babies [ 15 ] bring new importance to this aspect of salivary analysis [ 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 ].

Bicarbonate secretion is of tremendous importance to ruminants because it, along with phosphate, provides a critical buffer that neutralizes the massive quantities of acid produced in the forestomachs. Small collecting ducts within salivary glands lead into larger ducts, eventually forming a single large duct that empties into the oral cavity. Most animals have three major pairs of salivary glands that differ in the type of secretion they produce:. The basis for different glands secreting saliva of differing composition can be seen by examining salivary glands histologically.

Two basic types of acinar epithelial cells exist:. Acini in the parotid glands are almost exclusively of the serous type, while those in the sublingual glands are predominantly mucus cells.

In the submaxillary glands, it is common to observe acini composed of both serous and mucus epithelial cells. In the histologic sections of canine salivary gland shown above, the cells stained pink are serous cells, while the white, foamy cells are mucus-secreting cells.