Skeletal muscle nitric oxide concentrations in normotensive and spontaneously hypertensive rats.

It is well established that there is a differential distribution of the nitric oxide synthases (NOS; neuronal, eNOS; inducible, iNOS and endothelial, eNOS) in skeletal muscle which differ in their quantitative expression depending on tissue and species. In humans, nNOS expression has been found to be similar in both type I and type II skeletal muscle fibers, while in rodents an increase in the expression of nNOS in type II fibers as compared to type I fibers has been observed. It has also been suggested that hypertension may alter the expression of nNOS in skeletal muscle, however, very few direct measurements of nNOS expression or nitric oxide (NO) concentrations have been made under these conditions. Therefore, the purpose of the present study was to determine NO concentrations in the white gastrocnemius (WG) and soleus (S) muscle of WKY (control) and spontaneously hypertensive rats (SHR). Basal WG NO levels were consistently lower, but not different (P>0.05) between WKY and SHR rats, While S NO levels were also similar between groups. However, the WKY and SHR groups showed a 27±7% and 11±3% higher (P<0.05) NO concentration in the WG as compared the S muscle, respectively. These data demonstrate that hypertension does not result in any significant changes in the basal levels of NO in rat WG and S muscle and may be explained by the fact these measurements were made on resting skeletal muscle. However, this study clearly showed a greater NO concentration in type II versus type I muscle fibers. Supported by NSERC [ABSTRACT FROM AUTHOR]