The Morphological Study On The Development Of Dairy Goat Mammary Gland

Mammary gland was an organ possessing significant economic value, whose development and lactation function was very close. Now there were only a few laboratories going in for foundational studies on mammogenesis in the world. Although the researches about mammogenesis and lactating mechanism had been carried out extremely early, very a few morphological studies on the development of mammalian mammary gland in different period, especially dairy goat. In this research, the study on the microstructure and ultrastructure and the changes of major tissue components in different period of dairy goat mammary gland were executed with laser Confocal microtechnique, TEM ultramicrotomy, Real-time PCR and histochemistry methods. The results were to provide the intimate data for the further research of the development and function of dairy goat mammary gland.In this research, HE dyeing and TEM ultramicrotomy were applied for the study on the microstructure and ultrastructure of dairy goat mammary gland. The results showed the mammogenesis of dairy goat was a successive process which included virgin, pregnancy, lactation, involution. The changes in morphology, histology and cytobiology during mammary growing approximately matched with else ruminant mammogenesis and differed from rodents.To formulate the changing rules of carbohydrates, lipids and proteins in different period of dairy goat mammary gland on the expression level and transcription level, the changes of lactose were detected with PAS, the changes of adipose tissue with oil red dyeing, the changes of milk proteins with ninhydrin-schiff dyeing, the change ofβ-casein with direct immunofluorescence, and the changes of related key genes of mammogenesis were detected with relatively quantitative analysis in our research. The results showed that (1) glucoproteins and proteoglycans were the major carbohydrate in virgin, early and mid- pregnancy and involution. Lactose was the hosr in late pregnancy and lactation. The changing rules of lactose and beta 1,4-galactosyltransferase, key enzyme of lactose synthesis, were with one accord approximately. Their expression was very low in virgin, increased step by step after mid-pregnancy and reached the peak in late-lactation, decreased quickly in involution and recovered to the level of virgin. (2) Virgin mammary gland was filled with adipose tissue holding rich triacylglycerol, and the expression of acetyl coenzyme A carboxylase alpha (ACACA) and hormone-sensitive lipase (HSL), key enzyme of fat metabolism, was very high, showing the fat metabolism was very active. During pregnancy and lactating, mammary epithelium cells were presenting the characteristics of secretion by degrees. Milk generating request the synthesis of generous milk fat, which induced ACACA advancing gradually after pregnancy and reaching the peak in late-lactation. Large adipose cells disappeared gradually and a great deal of lipid droplets were emerging in the epithelium cells. HSL descended quickly after pregnancy, and was keeping in low level during lactation, which both partly started fat mobilization and prevent the constructive fat of mammary gland from being degraded to keep the integrality of gland. In involution, lipid droplets of gland started to fuse with each other into large vacuolus adipocytes, and the gland was again in the state of sex maturity but not gestation. The expression of ACACA and HSL was very low at this time. (3) The main proteins were glucoproteins and proteoglycans in virgin, early pregnant and involuting mammary gland. Milk proteins were major in mid- and late pregnant and lactating mammary gland.(4)β-casein appeared mid-pregnancy during mammary growing, advanced gradually and reached the peak in lactation, and decreased step by step in involution. A bulk ofβ-casein cumulated inside alveolus epithelium cells not lumina during late-pregnancy because of micelle secretion. The expression ofβ-casein gene was very low in virgin, increased fast after early pregnancy. The level ofβ-casein was stable during lactation, and there was no difference among different time, however, the expression ofβ-casein gene had significant difference. It was concluded that the expression ofβ-casein were controlled by several mechanisms. The expression ofβ-casein and its gene beginned to descend gradually in early involution, however which had significant difference than that of virgin because of preparing for next gestation probably.In addition, the changes of mammary architecture during growing were observed with live cell fluorescent labeling and laser Confocal microtechnique on the subcellsular level in our research. The results showed that the changing rules of endoplasmic reticulum and mitochondria in mammary epithelium cells matched probably with the study of ultrastructure and the changes of milk components detecting with histochemistry ways. To maintain the normal activity and function of cells, there were still a certain proportion of organelles in epithelium cells of involution.