Genetic and maternal influences in rat models of spontaneous and salt-induced hypertension.

Genetic and maternal influences on hypertension were studied by comparing the SHR and SS/Jr inbred rat strains and their reciprocal F1 hybrids under identical conditions. When raised on a low salt (LS) diet (0.3% NaCl), SHR rats had higher systolic blood pressure (SBP) than SS/Jr rats by 9 weeks of age. Direct recordings from freely moving rats at 18-24 weeks confirmed this difference. Placement on a high salt (HS) diet (8% NaCl) at 5 weeks of age significantly increased SBP within 3 weeks in all groups, although the degree of increment was significantly smaller in SHR females. Inbred strains had higher SBP than their F1 hybrids when measured indirectly and directly from arterial cannulae. After exposure to HS diet, F1 females reared by SHR dams exhibited larger increments in SBP, greater weight loss, and greater debilitation and associated mortality than F1 females reared by SS/Jr dams. Differences between inbred strains and F1s maintained on LS diet were consistent with dominance for low BP, and differential genetic control of hypertension in each inbred strain. F1 differences demonstrated that maternal factors affected body weight in weanlings, pressor response to HS diet, and associated debilitation.