VStrastreeeturag andi Iwaorpkogpetrical Studies on the Endothelia ]

ABs'r-(Ac'r. The T.]ltrastructure of tht endothe}ial cclls of the deep circumflex iliac and caudal supcrficial cpigastric arteries suppiying thc abdomino-inguinal rnammary g]and of female Wistar ra{s was studied throughout the reproductive cycle with an electron micros ¢ ope and image ana]yzerand compared with that of mammary gland capillaries. The subendetheiial space of the arteries was broader at the virgin and pest-weanlng stagcs but narrower in pregnancy and lactation, In some rats, the endothelial cells of the arteries radiated some blunt processes inte the media threugh f,enestrations in the internal elastic lamina. The density of pinocytotic vesic]es (PV) in the arteries (number of PV pcr tsrn2of endothelial eyteplasm) signiflcantly increased uring pregnancy and reached its maximum value during lactalion, then sEEbsequently decreased uring the post-weaning stage, The matnrnary g]and capi]laries showed the rnaximum changes of PV during pregnancy and Iactatjon, with twofo}d and fourfo]d increases during the respec;tive periods, The density of mitochondria increased signlficantly in the caplllaries during prcgnancy and lactation. The ]ength of the niarginal folds and inicreyi]]ous processes increascd sign"'icanellr tiuring lacEatien in beth Lhe arteries and capillaries, and especial]y, increased twofold in the mammary gland capillaries. It is assumed that thc uItrastructural cl]anges of the endothelial cel]s of the artcries and capi]laries are ciosety associated during reproductive cycle with the functaonal demand of the marnmary gjands. KEy woRDs: artery, endothe]ia] eel!, mammary glund,