Contractile protein and myosin heavy chain isoform (MHCI) expression in vascular and visceral smooth muscle (SM) during fetal and postnatal life

Contractile protein and MHCI expression in vascular and visceral SM is developmentally regulated; but how their patterns of expression differ is not described. We quantified contractile proteins and MHCI in aorta (Ao), bladder (Bl) and myometrium (Myo) from female fetal (n=19, 72-140d; term=145d) and postnatal (n=25; 1-120d) sheep by measuring total (TP) and soluble (SP) protein contents (pg/mg wet weight), actjn, MHC and MHCI contents (pg/mg wet weight) by SDS-PAGE, and 200 kDa MHCI by Western analysis with SMj and MHC-B specific antisera. Ao proteins gradually rose from s 100d gestation (n=6) to 3mos postnatal (n=9): TP from 65±6 [SEM] to 92±8 (R=0.40 ), SP 37±3 to 58±5 (R=0.48'), aeon 3.9±0.9 to 16±2 (R=0.6²⁺), and MHC 2.1±0.2 to 4.5±0.5 (R=0.5²⁺). Bl proteins rose (ANOVA'J before birth and were then unchanged: TP from 46±7 (s100d gestation, n=6) to 78±4 (130-140d gestation, n=8) to 81±6 (3mos postnatal, n=9); SP 38±5 to 58±5 to 69±5, and actin 4.4±0.3 to 12±2 to 19±1; MHC, however, gradually rose from 2.6±0.2 to 6.5±0.6 (R=0.6²⁺). 204 kDa MHCI content in Ao and Bl rose 4.3- (R=0.68 ) and 1.5-fold (R=0.58 ), respectively, by 3mos. While total Ao 200 kDa MHCI was unchanged (1.4±0.1) during development SM; rose 80% and MHC-B fell. Conversely, Bl 200 kDa MHCI content rose 3-fold by 3mos (R=0.64 ); MHC-B was never detected. Changes in Myo protein paralleled those of Ao. Ao and Myo proteins and MHCI gradually rise during ovine development, whereas Bl proteins rise before birth and nonmuscle MHCI is absent. Differences in expression may reflect differing function of SM types during development "p<0.007.