Metabolic Clearance of Rat Prolactin in the Lactating and Non-Lactating Rat

Grosvenor, Clark E.; Mena, Flavio; Whitworth, Neil S.

doi:10.1677/joe.0.0730001

Cited by 13 publications

(8 citation statements)

References 23 publications

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“…It has been demonstrated, by changing the dose infused, that the MCR of prolactin in urethane-anaesthetized lactating and non-lactating rats can change measurably within a few minutes (Grosvenor et al 1977) so that a change in clearance would have been detectable in the present work. The lack of any substantial alteration in MCR due to urethane anaesthesia suggests that studies of prolactin clearance mechanisms in urethane-anaesthetized rats can reflect accurately similar processes occurring in the conscious animal.…”

Section: Discussionmentioning

confidence: 61%

“…However, rather than being raised, the metabolic clearance rate was slightly, though not significantly, lower when compared with that of rats in mid-lactation. It has been shown (Grosvenor, Mena & Whitworth, 1977) that the MCR of prolactin is higher in lactating than in non-lactating rats. The present data would suggest that once this increased MCR occurs it remains stable during lactation.…”

Section: Discussionmentioning

confidence: 99%

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Secretion Rate and Metabolic Clearance Rate of Prolactin in the Rat During Mid- And Late Lactation

Grosvenor¹,

Whitworth²

1979

Journal of Endocrinology

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The prolactin concentration in the plasma of lactating rats rose less rapidly and attained a significantly lower plateau level in response to suckling on day 20--21 of lactation than it did on day 13--14 of lactation. Neither differences in suckling stimulation of the older pups nor a higher metabolic clearance rate (MCR) of prolactin were implicated in the reduced prolactin concentration seen in the late-lactating rats. The MCR was, in fact, slightly reduced in both conscious and late-lactating rats anaesthetized with urethane when compared with those in mid-lactation. The MCR of prolactin was not significantly altered by urethane anaesthesia in rats on either day of lactation. However, the secretion rate of prolactin, computed from the MCR multiplied by the equilibrium concentration of prolactin during suckling, was considerably reduced (665 to 392 ng/min) from mid- to late lactation. We conclude from these data that the reduced plasma concentration of prolactin in response to suckling in late lactation is the result of an impairment within the prolactin secretory mechanism.

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Section: Discussionmentioning

confidence: 61%

Section: Discussionmentioning

confidence: 99%

Secretion Rate and Metabolic Clearance Rate of Prolactin in the Rat During Mid- And Late Lactation

Grosvenor¹,

Whitworth²

1979

Journal of Endocrinology

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“…It is also possible that factors other than DA may contribute to the changes in plasma PRL levels in repro ductively experienced females. For example, circulating levels of PRL are affected by the animal's metabolic clear ance rate which changes as a function of the animal's reproductive and neuroendocrine states [14,15], PRL lev els in plasma are also affected by shifts in the responsive ness of the pituitary to endogenous inhibitory and stimula tory factors. An increase in metabolic clearance rate or a diminished release of PRL-stimulating factors, i.e.…”

Section: Discussionmentioning

confidence: 99%

Reproductive Experience Reduces Haloperidol-lnduced Prolactin Secretion in Female Rats

Bridges

Henriquez²,

Sturgis³

et al. 1997

Neuroendocrinology

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The present study examined possible changes in the dopaminergic regulation of prolactin (PRL) secretion which have been reported to occur in reproductively experienced female rats. In the first experiment, female rats which had raised a litter to weaning and age-matched nulliparous controls were ovariectomized and challenged sequentially 2 days apart with a low (0.2 mg/kg) and high (1.0 mg/kg) dose (intravenously) of haloperidol (HAL), a dopamine antagonist. Blood samples were collected via intra-atrial catheters, and plasma samples were assayed for PRL content by radioimmunoassay. Whereas HAL stimulated increases in plasma PRL concentrations in both nulliparous and primiparous animals, significantly higher levels of plasma PRL were present after both doses of HAL in the nulliparous rats. A second experiment investigated the role of lactation in this change in the ability of HAL to stimulate increases in circulating PRL levels. Separate sets of age-matched primiparous (pups removed on day 1 of lactation) and nulliparous rats were challenged with two doses of HAL 2 weeks after gonadectomy. In contrast to the effect of pregnancy and lactation found in the first experiment, pregnancy and parturition in the absence of lactation failed to alter the female’s sensitivity to HAL. The PRL responses in the two groups were identical at the low HAL dose and similar after the high HAL dose. These findings demonstrate that a single prior pregnancy and lactation, but not pregnancy alone, significantly reduce the ability of HAL to elevate circulating plasma PRL concentrations. Decreased circulating PRL levels in reproductively experienced females, therefore, may result in part from increased endogenous dopaminergic activity/tone.

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“…During suckling in mid-lactation, prolactin is cleared from the circulation at a rate of about 1 ml/100 g body weight/min (Grosvenor and Whitworth, 1974;Grosvenor et al, 1977;Mattheij and Nicoll, unpublished). This implies that during suckling considerable amounts of prolactin are released continuously from the pituitary.…”

Section: Discussionmentioning

confidence: 99%

The Suckling-Induced Rise of Plasma Prolactin in Lactating Rats: Its Dependance on Stage of Lactation and Litter Size

Mattheij¹,

Gruisen²,

Swarts³

1979

Horm Res

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The response of plasma prolactin to vigorous suckling was measured in lactating rats which had been isolated for 10-12 h from their offspring. Plasma prolactin was investigated during suckling at various stages of lactation. The results demonstrate that prolactin responds maximally to suckling already in the first days of lactation. In the second half of the lactation period, the prolactin rise in the plasma induced by suckling decreases gradually; this is not due to a reduced suck-intensity of older pups. A relationship is found between the height of the suckling-induced prolactin rise and litter size. The data suggest that during suckling in the first weeks of lactation the pituitary secretes large amounts of prolactin at a constant rate. It is speculated that in the first minutes of suckling, receptors may clear considerable amounts of released prolactin from the circulation.

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Metabolic Clearance of Rat Prolactin in the Lactating and Non-Lactating Rat

Cited by 13 publications

References 23 publications

Secretion Rate and Metabolic Clearance Rate of Prolactin in the Rat During Mid- And Late Lactation

Secretion Rate and Metabolic Clearance Rate of Prolactin in the Rat During Mid- And Late Lactation

Reproductive Experience Reduces Haloperidol-lnduced Prolactin Secretion in Female Rats

The Suckling-Induced Rise of Plasma Prolactin in Lactating Rats: Its Dependance on Stage of Lactation and Litter Size

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