RESULTADO DE PESQUISA DO PUBMED

IMPACT OF CARDIAC HYPERTROPHY ON ARTERIAL AND CARDIOPULMONARY BAROREFLEX CONTROL OF RENAL SYMPATHETIC NERVE ACTIVITY IN ANAESTHETISED RATS.

Flanagan ET, Buckley MM, Aherne C, Lainis F, Sattar M, Johns EJ.

University College Cork.

This study aimed to quantify the effect of isoprenaline/caffeine induced cardiac hypertrophy on reflex regulation of renal sympathetic nerve activity by the arterial and cardiopulmonary baroreceptors. Male Wistar rats, either untreated or given water containing caffeine and sc isoprenaline every 72h for 2 weeks or thyroxine sc for seven days, were anaesthetized and prepared for measurement of renal sympathetic nerve activity or cardiac indices. Both isoprenaline/caffeine and thyroxine treatment blunted weight gain but increased heart weight, heart weight/body weight ratios, by 40 and 14% (both P<0.01), respectively. In the isoprenaline/caffeine group, max dP/dt and contractility index were higher by 17 and 14% (both P<0.01), respectively, compared to untreated rats. In the isoprenaline/caffeine treated rats, baroreflex gain curve sensitivity was depressed by approximately 30% (P<0.05) while the mid-point blood pressure was lower, by 15% (P<0.05), and the range of the curve was 60% (P<0.05) greater than in the untreated rats. The acute saline volume expansion decreased renal sympathetic nerve activity by 42% (P<0.05) in the untreated rats but had no effect in the isoprenaline/caffeine or the thyroxine treated groups. The isoprenaline/caffeine treatment induced cardiac hypertrophy with raised cardiac performance and an associated depression in the reflex regulation of renal sympathetic nerve activity by both high and low pressure baroreceptors. The thyroxine induced cardiac hypertrophy also blunted the low pressure barorecepotr mediated renal sympatho-inhibition. These findings demonstrate that in cardiac hypertrophy without impaired cardiac function, there is a blunted baroreceptor control of renal sympathetic outflow.

PMID: 18487313 [PubMed - as supplied by publisher]