Sex-specific decrease in maximum isometric force-generating capacity in nNOSμ-deficient skeletal muscle.

<p>Maximum isometric force output (P_o) from TA muscles of 8 week old adult male (M) and female (F) mice homozygous for the wild type <i>NOS1</i> allele (+/+) or or <i>NOS1</i> null allele (−/−) is shown in A. P_o was significantly decreased (p<0.01) in male KN1 TA muscle compared with sex-matched littermate controls (A). Wild type male mice generated greater total force than wild type female mice (p<0.01). Maximum tetanic force output from female TA skeletal muscle was unaffected by the absence of nNOSμ (A). Specific force (sP_o), maximal tetanic force output normalized for the length and mass of the TA muscle, was not significantly affected by the absence of muscle nNOSμ in both males and females (B). Force-frequency profiles for wild type (black circles) and KN1 mice (grey squares) are shown in C. Males and females are pooled into wild type and KN1 groups. There was no difference in the force-frequency curves between KN1 males and their littermate controls suggesting no gross abnormalities in neuromuscular transmission. Numbers of animals analyzed: 15 wild type (8 males and 7 females) and 15 KN1 (7 males and 8 females). Values shown are mean±standard error of the mean (S.E.M).