Hormone studies in Myxine glutinosa: effects of the eicosanoids arachidonic acid, prostaglandin E1, E2, A2, F2 alpha, thromboxane B2 and of indomethacin on plasma cortisol, blood pressure, urine flow and electrolyte balance.

Abstract

Hagfish, Myxine glutinosa, were used in an investigation of the possible effects of various eicosanoids and the prostaglandin synthetase inhibitor indomethacin, on cortisol production, blood pressure control, urine flow and electrolyte balance. Cortisol levels in plasma of untreated control animals and plasma from animals 1 h following injection of 50 micrograms kg-1 prostaglandin E1, E2, A2, F2 alpha TXB2 and indomethacin were not detectable. However, plasma cortisol levels rose to between 10 and 26 pg ml-1 1 h following injection of either 50 micrograms kg-1 arachidonic acid or prostaglandin E2. This rise was similar in magnitude to that produced 1 h following administration of 50 micrograms kg-1 porcine ACTH. The resting dorsal aortic blood pressure of between 3.50 and 3.75 mmHg was reduced on average by 50% for 12-15 min when animals received 10 micrograms kg-1 arachidonic acid, prostaglandin E1, E2, A2, and TXB2 and was effectively reduced to zero for 20 min or more following 50 micrograms kg-1 of these eicosanoids. Similar doses of prostaglandin F2 alpha, however, evoked an increase in blood pressure (19-33%) whilst indomethacin was without effect. Control measurements of urine flow in Myxine were estimated to be between 540 and 660 microliters h-1 kg-1. There was a marked reduction in urine output following the arterial vasodepression induced by arachidonic acid, prostaglandin E1, E2, A2 and TXB2 in doses of 10 micrograms kg-1, an effect which became even more pronounced following injection of 50 micrograms kg-1 quantities, leading in some cases to complete anuria.(ABSTRACT TRUNCATED AT 250 WORDS)