Changes in density and architecture of microvessels of the rat mammary gland during pregnancy and lactation.

Abstract

Summary. This paper deals with changes in intralobular microvascular density and architecture of the rat mammary gland during the reproductive cycle.Morphometrical analysis of india ink-perfused histological sections showed that the vascular density (the percentage of the total area of the vascular lumen to the whole lobular area), was consistently low before pregnancy and slightly increased by the 5th day of gestation. The vascular density increased twofold from the 5th to 10th days and decreased gradually thereafter. This substantial increase may presumably be associated with rapid glandular development, and the subsequent decrease may reflect the hypertrophy of individual acini.Scanning electron microscopy of corrosion casts showed that blood vessels were sparse before the 5th day of gestation and proliferated by capillary sprouts and globular outgrowths of venules by the 18th day. After the 12th day, the blood vessels were organized into round lumps which appeared to correspond in size to individual lobules. By the 18th day, the vessels were remodeled into highly ordered basket like units which disintegrated by the 20th day. The findings suggest that homogenious acini, formed temporally, eventually undergo uneven growth.

Differential Recruitment of T- and IgA B-lymphocytes in the Developing Mammary Gland in Relation to Homing Receptors and Vascular Addressins

“…These results are in agreement with the reports on developing vascularization in the rat MG (Yasugi et al 1989).…”

Vascular remodelling during the normal and malignant life cycle of the mammary gland

“…Thus, the rapid increase in the number of capillaries in early pregnancy is achieved by sprouting angiogenesis. In midgestation around day 14, a basket-like organisation of the capillary network develops corresponding in size and extent to the individual epithelial alveoli, reflecting the formation of vascular "honeycombs" around the developing alveoli (Matsumoto et al, 1992;Yasugi et al, 1989). Furthermore, the number of capillary sprouts decreases and in later stages of pregnancy capillary sprouts disappear completely ( Fig.…”

Regulation of Mammary Development as It Relates to Changes in Milk Production Efficiency

“…Uptake of nutrients, and subsequent synthesis of milk components, is dependent on the rate of blood flow through the capillaries surrounding each alveolus, and also the exchange of nutrients across the capillary wall (Prosser et al, 1996). During pregnancy, the number of blood vessels in the mammary gland gradually increases as the gland prepares for copious milk production (Yasugi et al, 1989;Matsumoto et al, 1992;Djonov et al, 2001). During established lactation, the vasculature is maintained and then slowly regresses with advancing lactation and involution.…”