Spontaneously occurring hypertension in wild Rhesus monkeys.

In this study naturally occurring hypertension in wild rhesus monkeys has been noted with a frequency of 13 out of 428 monkeys examined. The maximum systolic/diastolic blood pressure was 242/140 mm of Hg. Clinically there was evidence of grade I retinopathy in one case only, otherwise the animals did not manifest any symptom to suggest illness. Biochemical examination revealed normal plasma angiotensin activity but the level of serum sodium was slightly elevated. The serum potassium, blood urea and serum creatinine values were within normal limits. Serum cholesterol was, however, elevated in two cases. All hypertensive animals were sacrificed by exsanguination and a complete autopsy was performed. It revealed left ventricular hypertrophy in almost all cases, patchy myocardial degeneration with fibrosis in 3 animals and advanced renal disease only in 3 cases. It therefore appears that most of these cases of hypertension belonged to the idiopathic group.