Adrenal cortex contributes to the regulation of NaCl‐stimulated ANP release in the rat

Abstract

The present study documents the effects of hypophysectomy and the effects of dexamethasone substitution on the NaCl-stimulated release and on the basal secretion rates of ANP from the rat atria in vitro. We also measured the concentration of mRNA in the atria after hypophysectomy. Rats (n = 12) were subjected to hypophysectomy by a parapharyngeal approach. One group of rats (n = 6) received dexamethasone 0.2 mg s.c. daily for 4 weeks, while the other group was left unsubstituted. After 4 weeks, the atrial block (n = 10) was excised, placed in an organ bath (field stimulation 4 s-1, 20 V, 1 ms; resting tension = 5 mN) and superfused (7 ml min-1) either with a physiological buffer solution (295 mosmol kg-1) or with a hyperosmotic NaCl solution (330 mosmol kg-1). The atria from the hypophysectomized rats did not respond to the stimulus: the concentration of ANP in the 1-min samples of the perfusate was under 100 pg ml-1. Dexamethasone treatment significantly (P less than 0.05) increased the ANP concentration to a maximum of 165 +/- 17 (mean +/- SEM) pg ml-1 during the superfusion while the control concentration was 110 +/- 19 pg ml-1. The ANP mRNA/18 S RNA ratios did not differ between the atria of hypophysectomized and control rats. In conclusion, glucocorticoids are required in the stimulus-induced release of ANP and the impaired release of ANP after hypophysectomy does not depend on an impaired synthesis of ANP.

Involvement of plasma atrial natriuretic peptide in protracted alcohol withdrawal

“…However, in our study patients with delirium tremens were excluded and no patient developed any signs of hyperhydration. While blood osmolarity has also been shown to influence ANP levels (36,37), electrolyte concentrations in our sample were shown to be in the normal range. Hence, changes of blood volume or osmolarity do not seem to be responsible for our findings.…”

Daily patterns of plasma atrial natriuretic peptide, serum osmolality and haematocirt in the rat

“…We have shown previously that increased osmolality enhances the release of ANP from isolated rat atria (Arjamaa & Vuolteenaho 1985, Arjamaa 1989, Arjamaa et al 1990 circumstances in which no change in stretch occurs. Isolated atrial myocytes a k o secrete ANP in response to osmotic stimuli (Gibbs 1987).…”