Relative Capillary Blood Flow and Leydig Cell Function in Old Rats

Pirke, Karl M.; Bofilias, I.; Sintermann, R.; Langhammer, H.; Wolf, Ingo; Pabst, Hans W.

doi:10.1210/endo-105-3-842

Cited by 24 publications

(11 citation statements)

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“…The rat is the most popular laboratory animal to examine the effects of aging on testicular androgen synthesis and secretion. A number of studies carried out during the past few decades have led to a clear demonstration that aging leads to significant reduction in blood testosterone levels in several rat strains [157][158][159][160][161][162][163][164][165][166][167][168][169].…”

Section: Experimental Animalsmentioning

confidence: 99%

Impact of Aging on Steroid Hormone Biosynthesis and Secretion

Zaidi¹

2013

TOLSJ

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Steroid hormones are lipophilic, low-molecular weight organic compounds all of which are derived from cholesterol. They are primarily synthesized by steroidogenic glands such as gonads (ovary and testis), the adrenal gland and, during pregnancy, by the placental trophoblasts. Limited steroid synthesis also takes place in the brain. Steroid hormones are crucial for the proper functioning of the body. They mediate a wide variety of vital physiological functions, ranging from maintaining normal reproductive function and secondary sexual characteristics, to regulating virtually every metabolic process in the body. Like many age-related endocrine disorders, aging also progressively impacts the tissue-specific synthesis and secretion of steroid hormones. The goal of this review is to summarize the effects of aging on steroid hormone synthesis and secretion by the adrenal gland and gonads of both human and experimental animal models, to describe the potential involvement of excessive oxidative stress in mediating age-related alterations in steroidogenesis, and to discuss the possible underlying mechanisms involved.

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Section: Experimental Animalsmentioning

confidence: 99%

Impact of Aging on Steroid Hormone Biosynthesis and Secretion

Zaidi¹

2013

TOLSJ

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“…All blood samples were allowed to clot at room temperature: the plasma was separated by centrifugation and stored at -20 "C until the LH RIA was per formed. LH was measured using reagents kindly provided by the Pituitary Agency of the National Institutes of Health [29]. LH va lues were expressed in terms of nanogram equivalents of LH-RP-I.…”

Section: In Vivo Experimentsmentioning

confidence: 99%

The Actions of Prostaglandin E<sub>2</sub>, Naloxone and Testosterone on Starvation-Induced Suppression of Luteinizing Hormone-Releasing Hormone and Luteinizing-Hormone Secretion

Küderling¹,

Dorsch²,

Warnhoff³

1984

Neuroendocrinology

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In man and other mammals, starvation is accompanied by a severe suppression of luteinizing hormone-releasing hormone (LHRH) and luteinizing-hormone (LH) secretion, which is caused by unknown alterations in hypothalamic functions. Prostaglandin E₂ (PGE₂), endorphins and testosterone (T) are know to be strongly involved in the regulation of LHRH release. The present study examined whether the influence of these substances on LHRH and LH secretion was affected by starvation. In vitro experiments checked the release of PGE₂ and LHRH from median eminences (ME) of fed male rats and ones starved for 5 days. Stimulation with potassium (80 mM) induced an equally strong release of PGE₂ and LHRH from the MEs of both fed and starved rats. When PGE₂ (10 ⁴M) was added to the superfusion medium, the potassium-stimulated release of LHRH was significantly enhanced in both groups of animals. The results clearly showed that in the terminal region of the hypothalamic LHRH system the release of this hormone and the action of PGE₂ were not altered by starvation. In vivo experiments tested whether the effects of LHRH, PGE₂, naloxone (NAL), or T on LH secretion were different in intact or castrated male’rats fed or starved for 3 and 5 days. LHRH (250 ng/kg) stimulated the same amount of LH secretion in fed and starved rats. The starvation-induced LH suppression was not due to a dysfunction at the pituitary level. The stimulatory action of PGE₂ (1 mg/kg) on LH was gradually reduced throughout the starvation period. NAL (5 mg/kg) had little, respectively, no effect on LH release on the 3rd or 5th day of starvation. When given simultaneously, NAL did not affect the action of PGE₂ in any of the three nutritional states. The interference of factors other than endorphins or PGE₂ is assumed for starvation-induced suppression of LH secretion. Starvation did not alter the influence of T (ca. 3 ng/ml plasma) on LH secretion at the pituitary level. The stimulatory effect of PGE2 on LH release was completely suppressed by T in fed, as well as in castrated rats starved for 3 or 5 days.

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“…LH in serum was measured using reagents kindly provided by the Pituitary Agency of the National Institute of Health. The method was described earlier (Pirke et al 1979c). The results were expressed in ng of LH-RP-1 standard per ml.…”

Section: Radioimmunoassaysmentioning

confidence: 99%

Effect of starvation on gonadotrophin secretion and on in vitro release of LRH from the isolated median eminence of the male rat

Warnhoff

Dorsch

Pirke

1983

Acta Endocrinologica

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A perfusion system was developed in which isolated median eminences (ME) were stimulated in vitro by depolarizing agents such as potassium and veratridine. Potassium concentrations between 30 and 80 mm released increasing amounts of luteinizing hormone\x=req-\ releasing hormone (LRH) from the MEs of starved and control rats. Veratridine at a concentration of 50 \ g=m\ m caused a more prolonged LRH release in both starved and control animals. LRH secretion in vitro was slightly, though not under all conditions, significantly greater in rats starved for 5days. The testosterone ((T)-LHck was studied by castra¬castra-ting the animals and substituting various doses of throuT implantation of T-releasT-reldifferent. The Tconcentration in plasma, which can prevent the castration-induceds much smaller in starved than in control rats. The in vitro release of LRH evoked by 80 mM potassium was not different for starved and fed rats under various feedback conditions. Both groups revealed decreased in vitro release of LRH when castrated animals were not substitutT.The effect of castration was studied from 1to 28 days.The plasma LH values rapidly increased in starved and control animals, indicating that the hypothalamic responsestration is not delayed by starvation. The release in vitro of LRH decreased from the firsthe fifthand remained constant thereafter. No significant difference between starved and fed rats was observed. The experiments indicate that the 'releasable pool' of LRH in vitro is greater under conditions of reduced LH release in vivo. The basic mechanism of depolarization-inducedm the ME is intact in starved animals.

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Relative Capillary Blood Flow and Leydig Cell Function in Old Rats

Cited by 24 publications

References 0 publications

Impact of Aging on Steroid Hormone Biosynthesis and Secretion

Impact of Aging on Steroid Hormone Biosynthesis and Secretion

The Actions of Prostaglandin E<sub>2</sub>, Naloxone and Testosterone on Starvation-Induced Suppression of Luteinizing Hormone-Releasing Hormone and Luteinizing-Hormone Secretion

Effect of starvation on gonadotrophin secretion and on in vitro release of LRH from the isolated median eminence of the male rat

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