The effects of substance P and related peptides on alpha-amylase release from rat parotid gland slices.
1 The effects of substance P and related peptides on amylase release from rat parotid gland slices have been investigated. 2 Supramaximal concentrations (1 microM) of substance P caused enhancement of amylase release over the basal level within 1 min; this lasted for at least 40 min at 30 degrees C. 3 Substance P-stimulated amylase release was partially dependent on extracellular calcium and could be inhibited by 50% upon removal of extracellular calcium. 4 Substance P stimulated amylase release in a dose-dependent manner with an ED50 of 18 nM. 5 All C-terminal fragments of substance P were less potent than substance P in stimulating amylase release. The C-terminal hexapeptide of substance P was the minimum structure for potent activity in this system, having 1/3 to 1/8 the potency of substance P. There was a dramatic drop in potency for the C-terminal pentapeptide of substance P or substance P free acid. Physalaemin was more potent than substance P (ED50 = 7 nM), eledoisin was about equipotent with substance P (ED50 = 17 nM), and kassinin less potent that substance P (ED50 = 150 nM). 6 The structure-activity profile observed is very similar to that for stimulation of salivation in vivo, indicating that the same receptors are involved in mediating these responses. 7 All the fragments of substance P tested were capable of eliciting a full amylase release response. This indicates that the apparent partial agonist action of the C-terminal nonapeptide fragment on in vivo salivation is not explicable at the receptor level.
D000681:Amylases / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000502:physiology; D066298:In Vitro Techniques; D008297:Male; D010306:Parotid Gland / Q000187:drug effects / Q000201:enzymology*; D010455:Peptides / Q000494:pharmacology*; D051381:Rats; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects; D011976:Receptors, Muscarinic / Q000187:drug effects; D012472:Salivation / Q000187:drug effects; D013373:Substance P / Q000494:pharmacology*; D013748:Tetracaine / Q000494:pharmacology; D000516:alpha-Amylases / Q000378:metabolism*
D010455:Peptides; D011942:Receptors, Adrenergic, alpha; D011976:Receptors, Muscarinic; D013748:Tetracaine; D013373:Substance P; D000681:Amylases; D000516:alpha-Amylases; D002118:Calcium