The effects of high dietary lard on hypertension development in spontaneously hypertensive rats.

This study examined the effects of high dietary lard on the cardiovascular system responsible for regulating blood pressure in the spontaneously hypertensive rat (SHR), a model of essential human hypertension. The fat contents were 4.5% of diet weight for control diet and 20% for high-lard diet, respectively. Four-week-old male SHR animals were fed the diets for 9 weeks. After 9 weeks of feeding, the cardiovascular responses to the intravenous administration of vasoactive drugs were determined in conscious SHR animals. The pressor responses elicited by the α₁-adrenoceptor agonist phenylephrine were diminished in high-lard-fed SHR animals. The depressor responses elicited by the ß-adrenoceptor agonist isoproterenol were equivalent in the high-lard-fed SHR and control SHR groups. The depressor responses elicited by the nitric oxide donor sodium nitroprusside were equivalent in both dietary groups. The depressor responses elicited by the endothelium-dependent agonist acetylcholine were diminished in high-lard-fed SHR animals. Baroreceptor reflex-mediated changes in heart rates in response to changes in mean arterial blood pressure (MAP) elicited by phenylephrine and sodium nitroprusside were diminished in the high-lard-fed SHR group. Despite the diminished endothelium-dependent vasodilation and impaired baroreflex function, resting MAP values were similar in both dietary groups. These findings suggest that high dietary lard does not exacerbate hypertension in the SHR model.