Fluid and protein secretion by the submandibular glands of weanling rats in response to cholinergic and peptidergic agonists at various doses

Analysis of salivary flow rate, biochemical composition, and redox status in orchiectomized spontaneously hypertensive rats

OBJECTIVE

This study aimed to analyze the salivary flow rate, biochemical composition, and redox status in orchiectomized spontaneously hypertensive rats (SHR) compared to normotensive Wistar rats.

DESIGN

Thirty-two young adult male SHR and Wistar (3-months-old) rats were randomly distributed into four groups; either castrated bilaterally (ORX) or underwent fictitious surgery (SHAM) as Wistar-SHAM, Wistar-ORX, SHR-SHAM, and SHR-ORX. Two months beyond castration, pilocarpine-induced salivary secretion was collected from 5-month-old rats to analyze salivary flow rate, pH, buffer capacity, total protein, amylase, calcium, phosphate, sodium, potassium, chloride, thiobarbituric acid reactive substances (TBARs), carbonyl protein, nitrite, and total antioxidant capacity.

RESULTS

The salivary flow rate was higher in the Wistar-ORX compared to the Wistar-SHAM group, while remaining similar between the SHR-SHAM and SHR-ORX groups. ORX did not affect pH and salivary buffer capacity in both strains. However, salivary total protein and amylase were significantly reduced in the Wistar-ORX and SHR-ORX compared to the respective SHAM groups. In both ORX groups, salivary total antioxidant capacity and carbonylated protein were increased, while lipid oxidative damage (TBARs) and nitrite concentration were higher only in the Wistar-ORX than in the Wistar-SHAM group. In the Wistar-ORX and SHR-ORX, the salivary calcium, phosphate, and chloride were increased while no change was detected in the SHAM groups. Only salivary buffering capacity, calcium, and chloride in the SHR-ORX adjusted to values similar to Wistar-SHAM group.

CONCLUSION

Hypertensive phenotype mitigated the orchiectomy-induced salivary dysfunction, since the disturbances were restricted to alterations in the salivary biochemical composition and redox state.

Structure-activity relationships of sialogogic heptapeptides analogous to physalaemin

OBJECTIVES

The rationale behind this study was to determine in detail which amino acids in physalaemin are crucial to its sialogogue activity, with a view of synthesizing new sialogogues which might be of use in the treatment of dry mouth.

METHODS

With the progressive elimination of amino acids, one by one, from the C- and N-terminal regions, 126 heptapeptides were newly synthesized by the multipin peptide method, for comparison with II naturally occurring tachykinins.

RESULTS

The C-terminal amide in position II was essential for salivation, but not the pyrolidine group or the N-terminal amino acid residues in positions I to 4. In 18 heptapeptides in which M in position II (MII) was replaced by another amino acid, one by one, none caused salivation. In 18 heptapeptides, in which L10 or G9 was replaced, three peptides caused salivation but none had significantly increased secretory activities. In 18 heptapeptides in which Y8 was replaced, four caused salivation but only one (I) had significantly increased secretory activity. In 18 heptapeptides in which F7 was replaced, only Y caused salivation but with significantly reduced secretory activity. In contrast, in 18 heptapeptides in which K6 and N5 were replaced, most caused salivation and some of them had significantly increased secretory activities.

CONCLUSIONS

It is concluded that the sequence FYGLM-NH2 conserved in the C-terminal region of physalaemin is optimal, that amides in position II and F7 are very important for salivation, but that K6 and N5 can be replaced by some other amino acids, resulting in increased secretory activities.