Atrial natriuretic factor concentrations in discrete brain regions, pituitary, cardiac atria and plasma during the estrous cycle in rats.

Peripheral and central atrial natriuretic factor (ANF) concentrations were measured across the rat's estrous cycle. Vaginal smears were obtained from adult Sprague-Dawley rats maintained under controlled illumination (L/D: 14/10, onset 05.00 h). ANF concentrations in plasma, cardiac atria, pituitary and nine microdissected brain regions of females (n = 5-13) were determined by radioimmunoassay during either early proestrus (09.00-11.00 h), late proestrus (17.00-19.00 h), estrus (09.00-11.00 h), early metestrus (09.00-11.00 h) and late metestrus (17.00-19.00 h). Patterns of cyclic ANF immunoreactivity in plasma and atria were inversely related to each other, with plasma levels being significantly elevated during early metestrus when atrial levels were significantly decreased. Statistically significant central fluctuations in ANF levels during the estrous cycle were only found in the hypothalamic periventricular region (hPVA) and in the dorsal raphe (DR). ANF levels declined in both regions after late proestrus. Results indicate a relationship between ANF activity and cyclic patterns of fluid volume regulation and with phasic reproductive hormonal events.