Intracellular dynamics in pituitary mammotropes throughout the rat estrous cycle. II. Changes in synthetic and secretory organelles

Poole, Max C.; Mahesh, Virendra B.; Costoff, Allen

doi:10.1002/aja.1001580104

Cited by 13 publications

(10 citation statements)

References 29 publications

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“…The se rum prolactin values we are reporting 4 days after vagoto my are not typical of those found in rats with activated cor pora lutea [3,6]. Rats with activated corpora lutea show characteristic nocturnal and diurnal prolactin surges within 2 days of activation and elevated progesterone [6], During the estrous cycle [5,6], prolactin characteristically starts to rise early on the morning of proestrus. In the present study our rats, killed 4 days after surgery, would have been in pro estrus.…”

Section: Discussionmentioning

confidence: 91%

Abdominal Vagotomy Does Not Activate the Corpus luteum in Rats

Burden¹,

Lawrence²,

Louis³

et al. 1983

Neuroendocrinology

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Rats were vagotomized at proestrus and 4 days later serum prolactin and progesterone were determined by radioimmunoassay. The histology of the ovaries and the activity of ovarian Δ^5–3β-hydroxysteroid dehydrogenase (3β-HSD) were also studied. There was no difference between hormone values in sham and vagotomized rats 4 days after surgery. In addition, the ovarian histology and activity of 3β-HSD were similar in both sham and vagotomized animals. We conclude that vagotomy at proestrus does not interrupt estrous cycles by activating the corpus luteum.

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Section: Discussionmentioning

confidence: 91%

Abdominal Vagotomy Does Not Activate the Corpus luteum in Rats

Burden¹,

Lawrence²,

Louis³

et al. 1983

Neuroendocrinology

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“…Such an observation is not without precedent. Dramatic in vivo changes in mainmotroph volume have already been reported [24,25].…”

Section: Discussionmentioning

confidence: 93%

“…The use of morphometry to determine cell and organelle vol ume [40] is well recognized and has been used extensively by one of us (A.C.) to study the adenohypophysis [24][25][26]. In this instance, the sampling protocol consisted of making at least 500 sections of two or three blocks per pituitary from each experimental group.…”

Section: Quantitation Of Volume: Somatotroph Granule and Secondary mentioning

confidence: 99%

Structural Correlates of Stimulated and Inhibited Secretion: Electron Microscopic Observations of Somatotrophs in Perifused Rat Pituitary

Stachura

Costoff

Tyler³

1986

Neuroendocrinology

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The in vitro release of stored intracellular rat growth hormone (rGH) in response to several secretagogues suggests the functional division of rGH storage into at least two ‘compartments’ or ‘pools’. The first is an immediately releasable compartment whose response is brief. The second is a compartment which responds to more prolonged secretory demands. These observations are consistent with either a single, homogeneous population of somatotrophs, each of which exhibits functional compartmentalization of storage, or with heterogeneous populations of somatotrophs, each family of which provides one of the observed responses. We sought anatomical correlates of this functional compartmentalization using a perifusion/morphometric system which permitted examination of the first model while not excluding the second model. We selected for study an established perifusion protocol whose behavior was consistent and whose previous results suggested phases of both filling and emptying of the immediate release pool. Five parallel perifusions of pituitary fragments were run. The fifth perifusion was used to monitor rGH release and to confirm that the experiment had behaved in standard fashion. The first pituitary chamber was dismantled during basal perifusion to obtain tissue for microscopy, the next during exposure to 25 nM SRIF, the third during exposure to both 25 nM SRIF and 1 mM (Bu)₂cAMP, and the fourth shortly after the rapid release which followed SRIF withdrawal. Somatotroph granulation was decreased by 54% in the presence of SRIF, and then increased by 45% with the addition of (Bu)₂cAMP. The intracellular distribution of granules also fluctuated in relation to the stimulatory and inhibitory secretagogues. In addition, secondary lysosomes increased by 549% during SRIF-induced inhibition of rGH release. Cell volume was decreased by 37% in the presence of 25 nM SRIF; the addition of (Bu)₂cAMP did not reverse this SRIF effect. We conclude that the in vitro release phenomenon we have termed the ‘immediate release pool’ has an anatomic correlate in juxtamembrane granules, that inhibition of rGH release is accompanied by a significant increase in secondary lysosome activity, that while heterogeneous populations of somatotrophs probably exist, individual cells possess a range of responses consistent with functional compartmentalization, and that rGH release involves not only granule movement between anatomically demonstrable compartments, but in addition, major and rapid changes in somatotroph volume.

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“…The higher degree of emiocytosis at 04.00 h would indicate a release of PRL without an important previ ous granular storage state. In this regard, Poole et al [1980] studied the intracellular dynamics of PRL cells throughout the estrus cycle of the rat and found two peaks of serum hormone, separated by an interval of 6 h. These peaks were preceded by both high and very little storage of hormone, respectively.…”

Section: Discussionmentioning

confidence: 99%

“…Nowadays, quantitative ultrastructural analysis is considered a useful method to investigate cell activity [ Weibel, 1969], Moreover, it has been applied to the study of PRL-secreting cells under different experimental conditions [Herbert et al, 1977;Poole et al, 1980], including rhythmicity analysis [Batten and Ball, 1976;Souto and Gomez Dumm, 1981]. In this connection, the purpose of the present investigation deals with the morphometric study of PRL cells from normal male mice at different times of a 24-hour period, corre lated with the pattern of PRL serum concen trations during that period.…”

Section: Introductionmentioning

confidence: 99%

Prolactin Secretion in Normal Male Mice during a Circadian Period

Dumm¹,

M²,

Estivariz³

et al. 1983

Cells Tissues Organs

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A quantitative ultrastructural study on the prolactin (PRL) cells of normal male mice was correlated with serum PRL immunoassay determination at different times in a circadian period. Significant time fluctuations in the percentages of cytoplasmic volume occupied by most of the organelles, as well as cyclic variations in serum PRL concentrations were detected. The endoplasmic reticulum appeared more developed at the beginning of the light period, suggesting a higher synthesis of PRL at this time. The evaluation of the Golgi complex and the secretory granules would indicate that packaging of secretory material and storing of PRL granules ccurred mainly during the second half of the light period. This coincided with the lowest values in serum PRL concentration and an increment in mitochondrial mass. The highest emiocytotic activity together with a diminution of total secretory granules were found during the dark period. The peak of PRL serum concentration was also present in this phase, but some hours later. Evaluation of microtubules and lysosomes gave some additional information. The results are in keeping with those from some biochemical investigations performed in mice and rats, but are not in agreement with others. The importance of a morphometric approach to evaluate and corroborate the immunoassay methods in the study of cyclic hormone secretion is emphasized.

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Intracellular dynamics in pituitary mammotropes throughout the rat estrous cycle. II. Changes in synthetic and secretory organelles

Cited by 13 publications

References 29 publications

Abdominal Vagotomy Does Not Activate the Corpus luteum in Rats

Abdominal Vagotomy Does Not Activate the Corpus luteum in Rats

Structural Correlates of Stimulated and Inhibited Secretion: Electron Microscopic Observations of Somatotrophs in Perifused Rat Pituitary

Prolactin Secretion in Normal Male Mice during a Circadian Period

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