Rats with hypertension induced by in utero exposure to maternal low-protein diets fail to increase blood pressure in response to a high salt intake.

Hypertension in the rat has been demonstrated to be determined in utero by exposure to maternal low-protein diets. Assessment was made of the response of rats with maternal diet-induced hypertension to a chronic high intake of sodium chloride. Normotensive and hypertensive animals were provided with either drinking water (control) or 1.5% sodium chloride over a 7-day period. Normotensive rats significantly increased blood pressure in response to the increased salt intake. 5-7 days after the start of the study systolic blood pressure was 30-41 mm Hg higher than in controls. 7 days of salt drinking did not alter blood pressure in maternal low-protein diet-exposed, hypertensive rats. In both normotensive and hypertensive groups provision of 1.5% sodium chloride significantly increased fluid intake. In hypertensive rats in the increased fluid intake appeared to be an immediate response, whilst normotensive rats increased intake only after the first day. Urinary volume was increased in both groups of animals receiving salt, within 1 day, and Na+ excretion similarly increased by between 3.5- and 4.5-fold in both groups. K+ excretion initially decreased significantly in both normotensive and hypertensive rats drinking 1.5% sodium chloride, but returned to pre-salt drinking levels by day 5 of the experiment. Rats with maternal-diet-induced hypertension appear to be insensitive to the hypertensive effects of sodium chloride. This insensitivity does not appear to stem from a more rapid clearance of excess sodium, and may relate to other aspects of kidney function and metabolism.