EFFECT OF LOCAL HEATING OF THE SCROTUM, TESTES AND EPIDIDYMIDES OF RATS ON CARDIAC OUTPUT AND REGIONAL BLOOD FLOW

Abstract

Summary. The effects of immersing the scrotum, tail, testes and epididymides of rats in water at temperatures in the range 28 to 45° C on the cardiac output and blood flow through various tissues have been examined to assess the possible rôle of the cardiovascular system in the cytological responses of the testis to heat. The cardiac output recorded before immersion was 33·9 ± 0·8 (mean ±S.E.M.; 110 determinations) ml/100g/ min. Apart from the blood flow in the scrotal skin, the cardiovascular parameters were not consistently affected by temperatures of 28, 33, 37 and 40° C. The cardiac output was slightly elevated when the scrotum was immersed in water at 43 and 45° C, but blood flow through the brain, testes and all regions of the epididymides was markedly increased. Blood flow through the epididymal fat pad and mid-side abdominal skin was virtually unchanged at all temperatures. In contrast to all other tissues, the blood flow in the scrotal skin increased with temperature, being almost twice as great at 37° C as at 33° C, and with further increases at higher temperatures. There were no significant differences in cardiovascular parameters on immersing the tail alone in water at either 33 or 43° C. The results draw attention to the cardiovascular repercussions of immersing the scrotum of anaesthetized rats in water at high temperatures, and to the need for a re-evaluation of the cytological responses using more physiological temperatures.