Gonadotropin Levels in Lactating Rats: Effect of Ovariectomy12

Ford, J. J.; Melampy, R. M.

doi:10.1210/endo-93-3-540

Cited by 60 publications

(6 citation statements)

References 55 publications

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“…During early pregnancy, plasma prolactin level is elevated to ca. 3-fold that of diestrus, declines to a low level in mid-pregnancy, increases thereafter to reach a high maximum before mid and late lactation, and subsequently decreases (24)(25)(26)(27). The present investigation indicates that the increase of phospholipid, namely diacyl-GPE and diacyl-GPI, during lactation follows patterns of variation similar to those indicated in prolactin.…”

Section: Discussionsupporting

confidence: 72%

Changes in phospholipids and acyl group composition of rat mammary gland during pregnant, lactating, and post‐weaning periods

Sun

Leung

1976

Lipids

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The distribution of phospholipids as well as their fatty acid compositions of rat mammary tissues were examined during pregnant, lactating, and post-weaning periods. There was no apparent change in phospholipids and their acyl groups during the early and late pregnant periods. However, tissue phospholipid composition was different during pregnant, early, and late lactating periods. After parturition, there was a marked increase in the proportion of diacyl-glycerophosphorylcholine in the phospholipids of mammary tissue, but this proportion decreased gradually during lactation. The decrease in diacyl-glycerophosphorylcholine during lactation was marked by a corresponding increase in diacyl-glycerophosphorylethanolamie. Although the shorter chain fatty acids of triglycerides were increased during lactation, only a small proportion of these fatty acids was found in the phosphoglycerides. Marked changes in acyl group composition of individual phospholipids are found during these different physiological stages. In general, there was a rapid decrease in 20:4 and an increase in 18:2 in the major phosphoglycerides during parturition. The proportion of 20:4 in the phosphoglycerides remained low throughout the entire lactating period, while that of 18:2 continued to increase 2-3 fold. Most of the changes in acyl group of the phosphoglycerides during lactation returned to normal ca. 10 days after weaning. A possible relationship of the variation of phospholipid and acyl group compositions in mammary tissue to changes in hormonal pattern during different physiological stages is discussed.

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Section: Discussionsupporting

confidence: 72%

Changes in phospholipids and acyl group composition of rat mammary gland during pregnant, lactating, and post‐weaning periods

Sun

Leung

1976

Lipids

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“…The essential difference between the rats subjected to intense and to mild suckling was that, in addition to the degree of suckling stimulus, there was a significant increase in the level of prolactin in the former group (Ford & Melampy, 1973). The results of the present experiments demonstrate clearly that the true causative agent for effective block of LH secretion is prolactin, and not the intensity of suckling.…”

Section: Discussionmentioning

confidence: 44%

Induction and Inhibition of Implantation in Lactating Rats

Maneckjee¹,

Moudgal²

1975

Reproduction

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The interrelationship between prolactin and LH in the maintenance of pregnancy during lactation was studied. The reduction of suckled young from eight to two or less, as late as on the morning of Day 4 of pregnancy, resulted in normal implantation. Reintroduction of eight young on Day 4 to lactating pregnant rats deprived of their litters on Day 1 resulted in an inhibition of implantation, but reintroduction on Days 5 or 6 did not inhibit implantation. If oestrogen, HCG or PMSG was given on Day 4 of pregnancy, implantation was induced at the normal time in rats suckling large litters. When LH antiserum was given on the morning of Day 4 or Day 8 to pregnant rats suckling two young each, it blocked implantation and postimplantation survival of blasto-cysts, respectively. When the number of suckling young was increased from two to eight on Day 6, however, LH antiserum blocked pregnancy only to the extent of 70%. Prolactin administered during the preimplantation phase inhibited implantation in pregnant rats suckling a minimum number of young, but had no effect when given during the postimplantation phase. Progesterone failed to block implantation. Prolactin had no inhibitory effect on implantation in the absence of the suckling stimulus or in non-lactating pregnant rats. The inhibition of implantation by prolactin in rats suckling two young could be effectively reversed by the administration of oestrogen, PMSG or HCG on Day 4 of pregnancy.

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“…It was surprising that a 3-4-fold variation in natural litter size had no effect on the rate of lactose synthesis per g of tissue. Therefore, to the extent that the increased suckling of a large litter may elevate the plasma concentration of prolactin (Ford & Melampy, 1973), this hormone is not obviously regulatory in this capacity. The rather greater weight of mammary tissue seen in rats bearing larger litters may stem from a greater production of placental lactogen during pregnancy.…”

Section: Effect Oflitter Sizementioning

confidence: 99%

Lactose synthesis in the rat, and the effects of litter size and malnutrition

Wilde¹,

Kuhn²

1979

Biochemical Journal

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1. The rate of lactose synthesis per g of mammary tissue, measured in vivo by a radioisotopic technique, rose 13-fold between parturition and day 16 of lactation in the rat, but was unaffected by wide variation in litter size. 2. The increase reflected a greater tissue content of galactosyltransferase (EC 2.4.1.22), and was augmented by a rise in the total weight of mammary tissue. Superimposed on this were unpredictable changes in the functional efficiency of the enzyme. 3. Lactose synthesis in 14-day-lactating rats, permitted only 76% of the food intake of paired control rats over the previous 3 weeks, showed a pronounced diurnal variation at an overall rate markedly below that in control rats. 4. Such nutritional deficiency did not affect the tissue content of galactosyltransferase, but impaired its functional efficiency in a manner reversed by renewed feeding or by the preparation and incubation of acini in vitro. 5. Plasma insulin concentrations decreased at parturition and with increasing litter size, and remained relatively unchanged during lactation and malnutrition.

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Gonadotropin Levels in Lactating Rats: Effect of Ovariectomy12

Cited by 60 publications

References 55 publications

Changes in phospholipids and acyl group composition of rat mammary gland during pregnant, lactating, and post‐weaning periods

Changes in phospholipids and acyl group composition of rat mammary gland during pregnant, lactating, and post‐weaning periods

Induction and Inhibition of Implantation in Lactating Rats

Lactose synthesis in the rat, and the effects of litter size and malnutrition

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