Hemodynamic, renal, and steroidogenic actions of prostaglandins E1, E2, A2, and F2 alpha in European eels.

ABSTRACT

Seawater-adapted eels were implanted with both venous and arterial cannulae and catheterised. Prostaglandin in 0.9% glucose saline was given either by 10 microliters injection or by infusion (40 ng/min) while blood pressure recordings and blood samples were taken from the dorsal aorta. Glomerular filtration rates were calculated from the clearance of [3H]inulin, renal plasma flow from the clearance of PAH, and functional tubular mass from measurements of glucose reabsorption maxima (TmG). Cortisol levels were measured by radioimmunoassay. Injections of prostaglandin E1, E2, and A2 (0.01-10 ng/kg body wt) induced transient reductions in dorsal aortic blood pressure whilst concentrations of between 10 and 100 ng/kg body wt caused both prolonged vasodepression and glomerular antidiuresis, with decreased TmG and CPAH. Fractional excretion of electrolytes remained unchanged. Doses of 10-50 micrograms/kg body wt caused an initial glomerular diuresis, increased TmG and CPAH but were without effect on the fractional excretion of the filtered load. This diuretic action was followed by a longer period of antidiuresis. The vasodepression during 24 hr prostaglandin infusion became less severe after an initial 2-hr period, indicating a degree of tachyphylaxis. Prostaglandin F2 alpha in doses of 10-50 micrograms/kg body wt was slightly vasopressor but with no obvious effect on kidney function. All prostaglandins so far used, given either by infusion or injection caused a significant increase in cortisol production. These results suggest that prostaglandins may play similar roles throughout a range of vertebrates.