FUNCTIONAL-MORPHOLOGY OF LAMININ, COLLAGEN TYPE-IV, COLLAGEN BUNDLES,ELASTIN, AND PROTEOGLYCANS IN THE BULBUS-ARTERIOSUS OF THE WHITE BASS, MORONE-CHRYSOPS (RAFINESQUE)

Immunolocalization of the basal lamina proteins laminin and collagen t ype IV, and the distribution of collagen bundles, elastin fibres, and proteoglycans in the bulbus arteriosus of adult white bass, Morone ch sops, were investigated. The bulbus arteriosus consists of three disce rnible layers: intima, media, and adventitia. The media composes appro ximately 95 % of the bulbus arteriosus volume, and consists of elastin fibres, which allow distensibility, and proteoglycans which may be ut ilized in dissipating the frictional forces in an actively expanding b ulbus arteriosus. Laminin and collagen type IV were co-localized to th e luminal and bulbar-ventricular valve subendothelium anchoring the en dothelium to the underlying parenchyma. Laminin and collagen IV were a lso expressed in the adventitia along with prominent collagen bundles which may serve to limit the expansion of the bulbus arteriosus at hig h intraluminal pressures. Collagen bundles and scattered elastin fibre s are longitudinally aligned along the ventricular border of the bulba r-ventricular valve, acting as a semi-stiff border facilitating the ti mely opening of the valve and buffering the systolic force of inflowin g blood. Proteoglycans occupy the bulbar portion of the valve and are most probably involved in absorbing the initial recoil from the front of the valve, thereby decreasing wear and tear upon the valve.