The effect of salt hypertension on atherosclerosis in chicks fed mash without a cholesterol supplement.

With the technical assistance of P. Johnson Hypertension induced by adding sodium chloride to the diet (0.9 per cent) or drinking water (8 per cent) of chicks on plain mash did not intensify spontaneous atherosclerosis or lead to atherosclerotic lesions of the induced type. H YPERTENSION in man is typically associated with increased incidence and severity of atherosclerosis. Conversely, many people with atherosclerosis have hyper-tension.'-'3 However, longstanding hypertension may be unaccompanied by atherosclerosis, and atherosclerosis may develop in normotensive persons. Despite numerous clinical studies analysing and correlating these facts, the precise interrelationships between the two conditions, hypertension and atherosclerosis, remain obscure. This lack of clarity stems first of all from the inadequacy of our understanding concerning the pathogenesis of both hyper-tension and atherosclerosis. It is aggravated by the paucity of experimental investigations of the interrelationships between the two states. The meager laboratory data stand in marked contrast to the massive clinical findings. In view of this situation, we undertook to ascertain the effects of various forms of experimental hypertension on different types of experimental atherosclerosis. The present report presents our findings in one project of this series: a study of the effect of "salt" hypertension on atherosclerosis in the chick.14 15 METHODS Seventy-two 1 day old Hy-line cockerels were obtained from a certified hatchery and reared in a battery brooder. Upon receipt in the laboratory, these chicks were divided into three groups of 24 birds each. As indicated by the experimental regi-mens (table 1), substitution of 0.9 per cent saline solution for drinking water (group 1) and addition of up to 8 per cent salt to the mash. (group 2) were used to induce hypertension.16-20 The effect of this hypertension upon atherogenesis was assayed by comparison with a control group of chicks (group 3). Chicks were weighed weekly throughout the experiment. Blood pressures were determined serially after 8, 12, 17, 25 and 35 weeks on the experimental regimens. They were recorded in unanesthetized, quiescent chicks by direct puncture of a sciatic artery. At 8, 12, and 35 weeks, systolic and diastolic pressures were optically recorded with a Hamilton manometer.21 At 17 and 25 weeks, mean blood pressures were read off a mercury manometer. Comb size indexes were obtained periodically, using established methods for this measurement.22 * After 35 weeks of experimental feeding, birds from each group were killed by decapitation and exsan-guination. At sacrifice, plasmas from individual chicks were collected …