Superfused pituitary cell cultures: comparative responsiveness of cells derived from various stages of the estrous cycle to LHRH stimulation administered as short duration pulses

The Common Marmoset-Biomedical Research Animal Model Applications and Common Spontaneous Diseases

Marmosets are becoming more utilized in biomedical research due to multiple advantages including (1) a nonhuman primate of a smaller size with less cost for housing, (2) physiologic similarities to humans, (3) translatable hepatic metabolism, (4) higher numbers of litters per year, (5) genome is sequenced, molecular reagents are available, (6) immunologically similar to humans, (7) transgenic marmosets with germline transmission have been produced, and (8) are naturally occurring hematopoietic chimeras. With more use of marmosets, disease surveillance over a wide range of ages of marmosets has been performed. This has led to a better understanding of the disease management of spontaneous diseases that can occur in colonies. Knowledge of clinical signs and histologic lesions can assist in maximizing the colony's health, allowing for improved outcomes in translational studies within biomedical research. Here, we describe some basic husbandry, biology, common spontaneous diseases, and animal model applications for the common marmoset in biomedical research.

Acute, nongenomic actions of the neuroactive gonadal steroid, 3 alpha-hydroxy-4-pregnen-20-one (3 alpha HP), on FSH release in perifused rat anterior pituitary cells

We have previously shown that the gonadal and neurosteroid, 3 alpha-hydroxy-4-pregnen-20-one (3 alpha HP), can selectively suppress gonadotrophin-releasing hormone (GnRH) induced follicle-stimulating hormone (FSH) release from static cultures of anterior pituitary cells during a 4-h incubation period. The actions appeared to be at the level of the gonadotroph membrane and the cell signaling pathway involving Ca2+ and protein kinase C (PKC). In order to investigate further if the effects of 3 alpha HP on FSH release are generated by nongenomic mechanisms, we monitored the short-term effects of 3 alpha HP using dispersed anterior pituitary cells in a low dead-volume perifusion system with short (< or = 5 min) exposures to the steroid. Pulses of GnRH (10(-8) or 10(-7) M) lasting 2-5 min resulted in marked peaks of FSH release, and the variation in FSH amounts released from the cells in a particular column were minimal if the interval between successive GnRH pulses was at least 3-4 h. A 5-min pulse of 3 alpha HP (10(-9) M) administered simultaneously with the GnRH pulse suppressed GnRH-induced FSH release. On the other hand, similar treatment with the stereoisomer 3 beta-hydroxy-4-pregnen-20-one (3 beta HP), had no effect, but progesterone and estradiol pulses augmented the GnRH-induced FSH release. Pretreatment of cells with a 5-min pulse of 3 alpha HP, at 120, 60, or 30 min prior to a GnRH pulse suppressed the GnRH-induced FSH release. The suppression of GnRH-induced FSH release by 3 alpha HP was only partial if the start of the 3 alpha HP pulse occurred 0.5 or 1.0 min after the start of the GnRH pulse, and no suppression occurred if the start of the 3 alpha HP pulse was delayed by 2-5 min. The FSH release elicited by 5-min pulses of the Ca2+ ionophore A23187, the Ca2+ agonist BAY K8644, the PKC activator phorbol 12-myristate 13-acetate (PMA), or phospholipase C (PLC) was suppressed by simultaneous pulses of 3 alpha HP. The suppression of FSH release by 3 alpha HP appeared to be stereospecific, since no suppression was observed with 5 alpha-pregnane-3,20-dione (5 alpha P) or 3 alpha-hydroxy-5 alpha-pregnan-20-one (5 alpha P3 alpha). In separate experiments, cells were treated with pulses of BSA conjugates of 3 alpha HP, 3 beta HP, or progesterone; the 3 alpha HP-BSA, but not the 3 beta HP-BSA or the progesterone-BSA, suppressed the GnRH-induced release of FSH. The results of this study provide the first evidence that 3 alpha HP exerts immediate (nongenomic) and direct effects on GnRH-induced FSH release by interacting at the level of the pituitary gonadotroph membrane and the phosphoinositol cell signaling cascade involving Ca2+.

Estradiol and progesterone effects on relative luteinizing hormone and follicle stimulating hormone release induced from superfused anterior pituitary cell cultures by defined LHRH pulse regimens

These studies examined the capacity of estradiol and progesterone to modulate relative luteinizing hormone (LH) and follicle stimulating hormone (FSH) secretion from superfused anterior pituitary cells when stimulated with luteinizing hormone releasing hormone (LHRH) pulse regimens of specific amplitude, duration and frequency. There was particular interest in whether such steroid and LHRH treatments induced evidence of divergent LH or FSH secretion. Pituitaries were recovered from adult, 2 week ovariectomized rats and cultured for 48 h with collagen coated Cytodex microcarrier beads. Cultures were preincubated either with or without estradiol (1 or 10 nM) for 48 h and were subsequently incubated for 3,6 or 12 h with 100 nM progesterone. All groups were then pulsed with 1 of 3 LHRH regimens; regimen 1 delivered 8 ng in a single 100 microliters bolus once/h; regimen 2 divided the 8 ng dose of regimen 1 into 3 equal doses administered at 4 min intervals thereby maintaining the 8 ng mass of regimen 1 while extending the duration of exposure; regimen 3 was the same as regimen 2 except that the 3 equal doses were administered at a pulse frequency of 1 per 2 h rather than 1 per h thereby not only maintaining the duration of exposure as in regimen 2 but also reducing the pulse frequency. 1 nM estrogen alone for 48 h had no effect on LHRH stimulated LH release regardless of regimen; however, FSH was increased when hourly pulses of increased duration were applied (regimen 2). When estrogen was increased to 10 nM, regardless of regimen, LH was predominantly inhibited while FSH was unaffected. When 1 nM estrogen was followed by progesterone, both LH and FSH were elevated at 6 h progesterone in response to regimen 2; with 10 nM estrogen however, a divergent response was observed in that LH release was elevated at 6 h while FSH was elevated at 3 h in response to regimens 2 and 3. These results first of all confirm that progesterone in combination with estrogen is capable of exerting both inhibitory and stimulatory effects on gonadotropin secretion; secondly, these studies show that, as a direct pituitary effect, the LHRH regimen and the gonadal steroid milieu are capable of interacting to significantly influence the relative secretion of LH and FSH. The data therefore suggest that the divergent gonadotropin secretion seen in various physiological states in vivo is due likely in part to a combination of estrogen and progesterone priming in combination with the hypothalamic LHRH secretory pattern.

The induction of divergent gonadotropin secretion in vitro by variations in luteinizing hormone releasing hormone pulse regimen

The effects of luteinizing hormone releasing hormone (LHRH) pulse amplitude, duration, and frequency on divergent gonadotropin secretion were examined using superfused anterior pituitary cells from selected stages of the rat estrous cycle. Cells were stimulated with one of five LHRH regimens. With low-amplitude LHRH pulses (regimen 1) in the presence of potentially estrogenic phenol red, LH response in pituitary cells from proestrus 1900, estrus 0800, and diestrus 1,0800 were all significantly larger (P less than 0.05) than the other stages tested. In the absence of phenol red, responsiveness at proestrus 1900 was significantly larger than proestrus 0800, proestrus 1500, and estrus 0800 (P less than 0.01, 0.05, and 0.05, respectively); other cycle stages tested were smaller. No significant differences were observed between cycle stages for follicle-stimulating hormone (FSH) secretion in the presence or absence of phenol red. Because pituitary cells at proestrus 1900 were the most responsive to low-amplitude 4 ng LHRH pulses, they were also used to study the effects of LHRH pulses of increased amplitude or duration and decreased frequency. Increasing the amplitude (regimen 2) or the duration (regimens 3 to 5) increased FSH secretion; this effect was greatest with regimens 3 and 5. When regimens 3 and 5 were studied in pituitary cells obtained at proestrus 1500, FSH was significantly increased by both regimes, but most by regimen 5; furthermore, LH release was significantly reduced. When regimens 3 and 5 were studied in pituitary cells obtained at estrus 0800, FSH release was elevated most significantly by regimen 5. Thus, variations in LHRH pulse regimen were found to be capable of inducing significant divergence in FSH release from superfused anterior pituitary cells derived from specific stages of the estrous cycle.

Effect of luteinizing hormone releasing hormone pulse characteristics on comparative luteinizing hormone and follicle stimulating hormone secretion from superfused rat anterior pituitary cell cultures

We have shown that 4 ng luteinizing hormone releasing hormone (LHRH) pulses induced significantly greater luteinizing hormone (LH) release from proestrous rat superfused anterior pituitary cells with no cycle related differences in follicle stimulating hormone (FSH). Current studies gave 8 ng LHRH in various pulse regimens to study amplitude, duration and frequency effects on LH and FSH secretion from estrous 0800, proestrous 1500 and proestrous 1900 cells. Regimen 1 gave 8 ng LHRH as a single bolus once/h; regimen 2 divided the 8 ng into 3 equal 'minipulses' given at 4 min intervals to extend duration; regimen 3 gave the 3 'minipulses' at 10 min intervals, thereby further extending duration: regimen 4 was the same as regimen 2, except that the 3 'minipulses' were given at a pulse frequency of 2 h rather than 1 h. In experiment 1, all four regimens were employed at proestrus 1900. FSH was significantly elevated by all 8 ng regimens as compared to 4 ng pulses; further, 8 ng divided into 3 equal 'minipulses' separated by 4 min at 1 and 3 h frequencies (regimens 2 and 4) resulted in FSH secretion that was significantly greater than with either a single 8 ng bolus (regimen 1) or when the 'minipulses' were separated by 10 min (regimen 3). In experiment 2, at proestrus 1500, FSH response to the second pulse of regimen 4 was significantly greater than in regimen 2; LH release was significantly suppressed at pulse 2 compared to regimen 2 accentuating divergent FSH secretion. At estrus 0800, FSH response to the second pulse of regimen 4 was significantly stimulated FSH at proestrus 1900, 1500 and estrus 0800, FSH divergence was most marked at proestrus 1500. These data indicate a potential role for hypothalamic LHRH secretory pattern in inducing divergent gonadotropin secretion in the rat.

Cycle-related LHRH responsiveness of superfused pituitary cells in a Phenol red free medium

Anterior pituitary cell cultures are frequently used in studying the control of gonadotropin secretion. Historically, many (if not most) of these studies have been performed in the presence of Phenol red as a pH indicator. Phenol red preparations, because of their potential estrogenic activity, may have influenced the results of previous studies defining the relative luteinizing hormone releasing hormone responsiveness of rat anterior pituitary-cells derived from various stages of the estrous cycle. We therefore felt it of interest to investigate this possibility by repeating our previous cycle-related superfusion studies [(1988) Life Sci. 42, 61-72] in the absence of these Phenol red preparations. Comparisons of data obtained in the presence or absence of Phenol red revealed cells derived from late proestrous (19.00) and cultured in the absence of Phenol red continued to evidence the highest LH responsiveness. However, diestrous 1 08.00 cells cultured in the absence of Phenol red were lower in responsiveness than previously observed in the presence of the substance and the responsiveness of proestrous 08.00 and 15.00 in the presence was lower in comparison to the same stages in the absence of Phenol red. The results suggest that Phenol red preparations are capable of modulating LHRH responsiveness in superfusion and that the effect is more pronounced at certain cycle stages than at others.