SOLEUS MUSCLE CONTRACTILE PROPERTIES IN HYPERTENSIVE RATS

Three types of hypertensive rats, and their normotensive controls, wer e assessed to determine the effects of high blood pressure on the cont ractile and fatigue properties of the soleus muscle. Spontaneously hyp ertensive rat (SHR) soleus developed less contractile force and fatigu ed more rapidly than normotensive Wistar-Kyoto (WKY) controls. In cont rast, normotensive Wistar and Wistar-1 kidney/1 renal clip hypertensiv es were similar in their responses, and Dahl salt-sensitive hypertensi ves and Dahl salt-resistant controls also did not exhibit any signific ant differences in tension development or endurance. The results sugge st that the decreased ability to develop force and maintain it during stimulation may not be directly related to the high blood pressure in SHR. It may instead be related to a gene defect that cosegregates with the loci responsible for the rise in blood pressure. The reduced endu rance in SHR may be associated with an increased accumulation of K+ in the muscle during contraction, which decreases performance. It may al so decrease the ability of the vessels to dilate during muscle contrac tion,