Hemodynamic, renal, and steroidogenic actions of prostaglandins E 1, E 2, A 2, and F 2α 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 μl 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 E 1, E 2, and A 2 (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 μg/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 F 2α in doses of 10–50 μ/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.