THE INFLUENCE OF REPRODUCTIVE HORMONES ON ANF RELEASE BY RAT ATRIA

The effects of subcutaneous (sc) administration of estradiol (50 mug/100 mul/day x 10 day) or testosterone (15 mg/100 mul twice a week x 2 weeks) on ANF release were examined in isolated perfused rat atria. The concentration of ANF in the perfusate was measured by radioimmunoassay, under basal conditions (atrial wall unstressed), and during atrial distention (intraluminal pressure raised to 4, 6, and 10 cm water). In both male and female control (vehicle-injected) groups, increased atrial pressure resulting in distention of the atrium caused a significant increase in ANF release. Estradiol increased basal secretion of ANF but did not influence stretch-induced stimulation of ANF secretion. By contrast, although testosterone did not affect basal secretion, it completely abolished the stretch-induced increase in ANF secretion. Neither estradiol nor testosterone affected atrial compliance.