Lipid Transfer in Chicken Ovary
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Date
1981
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Department of Physiology and Biochemistry, College of Veterinary and Animal Sciences,Mannuthy
Abstract
The formation of an egg in the avian reproductive tract is a complex phenomenon. The exact mechanisms involved in the transfer of lipids synthesized in the liver and transported by blood to the ovary are not quite well understood. Hence this investigation was undertaken to study the various aspects of lipid transfer in relation to egg yolk formation. Ten numbers each of clinically healthy White Leghorn female birds of five different age groups (30 – 54- days, 70 – 74 – days, 100 – 104 – days, 129 – 133 – days and 223 – 227 – days – old) were selected at random, for the study and reared under standard farm conditions. Another group of 40 White Leghorn pullets (100 – 104 – days – old) were also selected at random and divided into four different groups of ten each. The first group of birds received stilbestrol dipropionate (SD), second group SD and progesterone (PG), the third group SD, PG, and testosterone dipropionate (TD) and the fourth group received olive oil alone for ten days consecutively. Blood serum, ovary and liver were collected from all the birds slaughtered by decapitation. Total lipid content in liver and ovary were determined by the method of Meynard and Joslyn (1970) and that in the serum, after extraction with ether and methyl alcohol. Phospholipid was estimated by adopting the method of King and Wootten (1959) and the total cholesterol by the method of Zak (1957). The growing birds recorded a progressive increase in phospholipids in the ovary, liver and blood serum. But the pullets treated with exogenous sex hormones did not show any significant increase in the level of phospholipids in the ovary while that in the liver and blood serum were high. The cholesterol level in the ovary, liver and bloods serum were high. The cholesterol level in the ovary, liver and blood serum were high in the different growing birds. But, here also, the cholesterol content in the ovary did not reveal any significant increase in level in pullets treated with different combinations of hormones, but that in the serum and liver were elevated. However, in the case of total lipids, the ovary, liver and blood serum in the case of all categories of birds showed a significantly higher content as age advanced and on the administration of hormones. The synthesis of lipids by the liver is increased in response to increasing levels of hormones as a result of growth and development of the birds. The lipids, synthesized in the liver, are distributed by the circulating blood to all the tissues, including the ovaries. The increase in concentration of lipids in the ovary as the birds grew older is due to the increased lipogenesis in the liver and their augmented transport by the blood. However, the pullets under the influence of exogenous sex hormones exhibited a different response. In the case of phospholipids and cholesterol the ovarian levels were low while in the liver and serum the values were high. The low levels of these components in the ovary may be due to the lesser ovarian activity induced by the operation of the negative feed – back mechanism between the pituitary and the sex steroids administered. But this does not hold good in the case of total lipids in the ovary of pullets receiving sex hormones. Here the level was high as in the case of liver and serum indicating a total absence of the operation of the negative feed – back mechanism. This calls forth further studies to enlighten the phenomenon.
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171507