Atrial natriuretic peptide and its mRNA in heart and brain of vasopressin-deficient Brattleboro rats.

To understand the secretion and synthesis of atrial natriuretic peptide we measured immunoreactive atrial natriuretic peptide from plasma, heart tissues and brain areas, and ANP mRNA was determined from heart auricles and ventricles of vasopressin-deficient Brattleboro rats (DI) and from desmopressin treated Brattleboro rats (DI+DDAVP). Long-Evans rats (LE) served as controls. DI+DDAVP rats were given for 3 days sc. injections of 0.5 micrograms 1-desamino-8-D-arginine vasopressin in 1 mL saline twice a day. The rats were housed in single metabolic cages and urinary output and water intake were measured daily. All the body and organ weight parameters were similar in the three groups when the rats were killed. No change was seen in the plasma ANP level between the groups. The right ventricle of DI+DDAVP rats had significantly (P < 0.05) higher concentration of ANP than LE rats (15.8 +/- 4.4 vs. 3.4 +/- 0.6 ng mg-1 tissue). The left ventricle of DI and DI+DDAVP had significantly (P < 0.05) lower amounts of ANP mRNA than LE rats (0.5 +/- 0.2 vs. 1.3 +/- 0.2 and 0.5 +/- 0.1 vs. 1.3 +/- 0.2 arbitrary units). In the hypothalamus, the ANP concentration was significantly (P < 0.05) lower both in DI and in DI+DDAVP rats than in LE rats (9.3 +/- 1.3 vs. 14.5 +/- 1.6 and 6.1 +/- 0.6 vs. 14.5 +/- 1.6 pg mg-1 tissue). To conclude, although the water intake and urinary output of DI rats were changed towards normal with desmopressin treatment, the heart ventricular and hypothalamic ANP did not parallel the change.(ABSTRACT TRUNCATED AT 250 WORDS)