ANALYSIS OF NITRIC OXIDE SYNTHASE AND MYOSIN HEAVY CHAIN ISOFORMS IN SKELETAL MUSCLE FROM HYPERTENSIVE AND NORMOTENSIVE RATS

 It has been reported that certain nitric oxide synthase (NOS; the enzyme that produces NO) isoforms, co-localize with particular myosin heavy chain (MHC; the protein that determines skeletal muscle fiber type) isoforms in skeletal muscle.  Therefore, the purpose of our study was to determine the extent of nitric oxide’s involvement in hypertension by determining relative levels of NOS and MHC using the spinotrapezius, a novel postural skeletal muscle model for a study of this type.  We hypothesize that the vasoconstriction associated with hypertension is due, in part, to reduced bioavailabity of NO in skeletal muscle tissue resulting from decreased NOS expression.  Bilateral spinotrapezius muscles from adult male Spontaneously Hypertensive Rats (SHR) and normotensive, Wistar Kyoto (WKY) control rats were removed.  One muscle was used to determine relative NOS levels using Western blot analysis, while the remaining muscle was used to determine relative levels of MHC isoforms by gel electrophoresis.  Preliminary Western blot data trends demonstrate relatively increased levels of all three NOS isorforms in SHRs vs. their WKY controls.  Similarly, preliminary gel electrophoresis data trends demonstrate relatively increased levels of the Type 1 (slow) MHC isoform in the SHR.  Further analysis will determine if these differences are statistically significant.  Surprisingly, the pilot data trends suggest NOS expression may be upregualted in hypertension as a compensatory mechanism for impaired vasoconstriction.  Parallel immunohistochemical experiments are being conducted to determine the extent to which each NOS isoform co-localizes with specific skeletal muscle fiber types.