The aim of this paper was to find out how
pulmonary arterial hypertension (PAH) affects heart rate in male and female rats. Additionally, the concentration of
tumor necrosis factor alpha (
TNF-alpha) was monitored. Male and female rats were treated by
monocrotaline (i.p., 60 mg/kg B.W.) or by equivalent volume of
normal saline solution (n=40) and after 4 weeks right auriculae containing sinoatrial cells have been isolated and examined. We have measured heart rate of spontaneously beating right auriculae and serum level of
TNF-alpha. In females with PAH,
isoprenaline curve was shifted to the left (pD2 increased from 10,9+/-3 to 15+/-3, n=10, P<0,05), but in males with PAH maximal acceleration of beating rate induced by
isoprenaline decreased from 175+/-10 to 146+/-8 beats/min, P<0.05). Additionally, reduction in heart rate induced by
rilmakalim was more significantly decreased in females (from -89+/-7 to - 49+/-3 beats/min, n=10, p<0.01) than in males (from - 68+/-6 to - 46+/-4 beats/min, P<0.05) with PAH. We did not detect any changes in
TNF-alpha in any experimental group. Our results imply that
pulmonary hypertension increased sensitivity of sinoatrial cells to
isoprenaline and decreased efficacy of
rilmakalim to reduce heart rate more significantly in females then in males.