NEUROSECRETION OF CRUSTACEAN HYPERGLYCEMIC HORMONE EVOKED BY AXONAL STIMULATION OR ELEVATION OF SALINE K+ CONCENTRATION QUANTIFIED BY A SENSITIVE IMMUNOASSAY METHOD

A sandwich-type enzyme-linked immunosorbent assay (ELISA) was utilized to quantify crustacean hyperglycemic hormone (as Carcinus maenas equi valents) released by single X-organ-sinus gland systems of the crab Ca rdisoma carnifex during continuous perifusion. Basal rates of secretio n (20-60 pg min(-1)) were stable for at least 4 h. Electrical stimulat ion (600 stimuli in 5 min) of the axon tract increased secretion two- to threefold, but only if it resulted in neural activity that was prop agated to the terminals of the sinus gland. No difference was observab le when stimuli were given repetitively or as a series of trains. Peri fusion with saline having ten times the normal K+ concentration augmen ted secretion by as much as fivefold. Augmented secretion of crustacea n hyperglycemic hormone evoked by either electrical or K+ stimulation appeared abruptly but declined slowly (over tens of minutes) after sti mulation was stopped. K+-evoked secretion of crustacean hyperglycemic hormone was maintained without decrement for at least 1 h. Basal secre tion increased in saline from which Ca2+ had been omitted, but decreas ed in saline containing Mn2+. Neither electrical stimulation nor high [K+] augmented secretion in Ca2+-deficient saline or if Mn2+ was prese nt. Introduction of Mn2+ during K+-evoked secretion immediately reduce d release to unstimulated levels; secretion resumed promptly upon remo val of Mn2+. Tetrodotoxin reversibly blocked both electrical and secre tory responses to axonal stimulation, but it did not block basal or K-evoked secretion. Release of crustacean hyperglycemic hormone by isol ated axon terminals was augmented two- to threefold by perifusion with saline having ten times the normal K+ concentration. The responses we re similar to those of the intact systems, having a rapid onset, well- maintained secretion and a long 'tail' of secretion after removal of t he K+ stimulus.