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Developmental changes in LH secretion by male pituitaries in vitro: from the infantile to adult period

J Bello-Pineda¹, J Luna, M C Romano

¹Department of Physiology, Biophysics and Neuroscience, CINVESTAV-IPN, México City, México.

The Journal of Endocrinology

|March 17, 1999

Insights

Male rat pituitary luteinizing hormone (LH) secretion differs with age. Infantile rats show a heightened, GnRH-sensitive LH response, suggesting a transitional developmental stage.

Area of Science:

Reproductive Endocrinology
Developmental Biology
Cell Biology

Background:

Luteinizing hormone (LH) is crucial for male reproductive functions.
Pituitary gland development and function undergo significant changes during postnatal maturation.
Understanding age-related changes in LH secretion is vital for reproductive health research.

Purpose of the Study:

To investigate age-related differences in LH secretion from male rat anterior pituitaries.
To characterize basal and gonadotropin-releasing hormone (GnRH)-stimulated LH release across postnatal development.
To examine morphological and functional characteristics of LH-secreting cells in infantile versus adult rats.

Main Methods:

In vitro incubation of anterior pituitary glands from rats at 14 (infantile), 23 (juvenile), 45 (pubertal), and 90 (adult) days old.
Measurement of basal and GnRH-stimulated LH secretion.
Primary cell cultures of infantile and adult pituitary cells to assess GnRH response.
Immunohistochemical analysis of LH-positive cells for morphology and distribution.

Main Results:

Basal LH secretion varied with age, with higher levels in juvenile and pubertal rats compared to infantile and adult.
Infantile pituitaries exhibited a significantly higher GnRH-induced LH secretory response than other age groups.
Infantile pituitary cells showed greater GnRH sensitivity and atypical cell morphology compared to adult cells, with a higher proportion of LH-positive cells.

Conclusions:

The infantile period represents a transitional stage in male rat pituitary development.
Two populations of LH-secreting cells may exist in the infantile pituitary: one mature and one with heightened GnRH sensitivity and distinct morphology.
These findings provide insights into the developmental plasticity of the hypothalamic-pituitary-gonadal axis.

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Abstract:

The secretion of LH from the anterior pituitary of male rats was studied at different periods of postnatal development. According to an established classification we used rats 14 (infantile), 23 (juvenile), 45 (pubertal) and 90 (adult) days old. By using an in vitro incubation system, both basal and stimulated LH secretion were studied in the same gland. Age-related differences were observed in basal LH secretion, with juvenile and pubertal pituitaries showing higher secretion compared with infantile and adult pituitaries. However, the GnRH-induced secretory response was significantly higher in the infantile rats than in other ages. LH secretion was also studied in primary cultures from infantile or adult pituitaries. In 24 and 48 h cultures, infantile cells showed a significantly larger response to GnRH than that of adult cells. In the infantile pituitary LH-immunopositive cells showed differences in size at different locations in the gland. At the periphery of the lobes the predominant cells were smaller and angular shaped, whereas in the center of the gland the majority of the cells were ovoid shaped. In the adult pituitary, the predominant LH-positive cells were ovoid in shape and larger in size. Furthermore, 10% more LH-positive cells were observed in infantile pituitaries. On the basis of these data we propose that at the infantile period the male rat pituitary has two populations of LH-secreting cells, one with adult secretory function and shape and a second with increased sensitivity to GnRH and with a morphology atypical of the adult cell. The results presented support the hypothesis that the infantile period is a transitional stage in the rat pituitary development.

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