Age-Related Changes in Secretion and Metabolic Effects of Atrial Natriuretic Factor in Rats

Abstract

The effects of aging on the secretion of and renal sensitivity to atrial natriuretic factor (ANF) were studied concomitantly in both senescent (25- to 34-month-old) and in adult (7- to 13-month-old) female and male Long-Evans rats. The plasma concentrations of ANF, measured in response to either a mild stimulation induced by a hypertonic volume expansion (i.e., 20 min after the onset of a continuous infusion during 15 min of a 2.5% NaCl solution; n = 18 old and 23 adult rats) or an intense stimulation produced by morphine injection (i.e., 30 min after an intraperitoneal injection of 5 mg morphine/100 g body weight; n = 11 old and 12 adult rats), were significantly lower (approximately -34 and -80%, respectively) in old as compared with adult animals. Acute intravenous injection of exogenous rat ANF (0.10 and 0.40μg/l00g body weight) induced similar natriuretic, diuretic, and kaliuretic effects in aged (n = 18) and in adult (n = 23) rats. The present data suggest that the significantly reduced (about -20%) natriuretic and kaliuretic responses of the aged rat, observed 20 min after the onset of hypertonic volume expansion, could be partly due to a primary defect in cardiac production and/or release of ANF rather than to a reduction of renal responsivity to ANF.

Renal Regulation of Potassium Homeostasis in Calves in the First Week of Life Including the Role of Atrial Natriuretic Peptide

“…Table 1 Filtered load of potassum (F K ), potassium tubular reabsorption (TR K ), potassium excretion in the urine (U•V K ), potassium clearance (C K ), blood plasma potassium concentration (P K ) in calves in the first week of life and significant differences (SD) between values in the following days of life The increase in potassium excretion in the urine observed in this experiment during the first week of life, as well as the previously noted increase in blood plasma ANP concentration with age (DRATWA 2006), but also the highest amount of potassium clearance observed with the highest blood plasma ANP concentration (DRATWA 2006), may imply (despite the lack of statistical significance) that ANP plays a role in regulation of potassium excretion in the urine. The increase in excretion of potassium in the urine after administration of exogenous ANP to animals, observed in adult dogs (KIMURA et al 1986), adult rats (RAKOTONDRAZAFY et al 1996), and in sheep fetuses (SHINE et al 1987), may confirm the above assumptions. Moreover, studies carried out on pups (AIZMAN et al 1998) and human neonates GARCÍA DEL RÍO et al 1982) preclude the direct involvement of aldosterone in the regulation of potassium excretion in the urine.…”