PREGNANCY IS ASSOCIATED WITH HYPOTROPHY OF CAROTID-ARTERY ENDOTHELIALAND SMOOTH-MUSCLE CELLS

It is known that blood how through the carotid artery is decreased dur ing pregnancy, which may be due to a pregnancy-associated increase in the sensitivity of this artery to vasoconstrictors. Recent studies hav e shown that alteration of blood how or pressure could remodel some ar teries over a short time frame. However, the possibility of remodellin g of the carotid artery during pregnancy has not yet been examined. Th erefore, the aim of the present study was to study the morphometrical and stereological characteristics of guinea-pig carotid artery during different stages of pregnancy (non-pregnant, early-pregnant, mid-pregn ant, late-pregnant, n = 8-10 for each group). The cross-sectional area of the different layers of the carotid artery and the cross-sectional area of endothelial and smooth muscle cells were measured using both light and electron microscopy, The values of internal diameter and cro ss-sectional area of adventitia were not significantly different, rega rdless of the pregnancy status, In contrast, external diameter, wall t hickness and cross-sectional areas of media and intima progressively a nd significantly decreased during pregnancy. In addition, volume/surfa ce density ratio of intima and media also significantly and progressiv ely decreased during pregnancy, suggesting hypotrophy of endothelial a nd smooth muscle cells of carotid artery. Indeed, electron microscopy revealed that the size, defined as cross-sectional area, of endothelia l and smooth muscle cells was significantly decreased during different stages of pregnancy, It is concluded that during pregnancy there is t hinning of the intimal and medial layers of guinea-pig carotid artery, which reflect pregnancy-associated hypotrophy of carotid artery endot helial and smooth muscle cells.