Biomedical subjects

K X Weiner

Publications and source records attributed to K X Weiner.

3 recordsLinked to original sources

PubMed1992

Developmental regulation of ornithine decarboxylase (ODC) in rat testis: comparison of changes in ODC activity with changes in ODC mRNA levels during testicular maturation.

These studies were undertaken to analyze the changes in testicular ornithine decarboxylase (ODC) mRNA levels and ODC activity in rats from birth to maturity. Levels of ODC mRNA were initially low in animals aged 10-17 days. Beginning at 21 days, ODC mRNA levels began to rise, reaching maximal levels by 40 days (p less than 0.01). The size of the 2.2- and 2.6-kb ODC mRNAs did not appear to change with age, as determined by Northern blot analysis. The increase in ODC mRNA that began at 21 days paralleled the increase in testis weight. This increase in ODC mRNA preceded the appearance of rat protamine-1 mRNA, a germ cell-specific mRNA found in round spermatids, which was first detected on Day 40. In contrast, levels of sulfated glycoprotein-2 mRNA, which, in the testis, is found exclusively in Sertoli cells, were highest at Day 17 and thereafter declined gradually with age. Unlike the increase in ODC mRNA levels, ODC activity was highest in 10-day-old animals and thereafter declined steadily with age, reaching minimal levels by 40 days (p less than 0.01). Thus, the increase in testicular ODC mRNA levels was in marked contrast to the decrease in testicular ODC activity. Incubation of cytosolic extract from 40-day-old animals with that from 10- or 17-day-old animals inhibited ODC activity approximately 50%, when compared to cytosols from 10- or 17-day-old animals. Dialysis of cytosol from 40-day-old animals prior to incubation with cytosol from 10-day-old animals relieved this inhibition.(ABSTRACT TRUNCATED AT 250 WORDS)

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PubMed1990

Protein synthesis is required for testosterone to decrease ornithine decarboxylase messenger RNA levels in rat Sertoli cells.

We have previously shown that pretreatment of Sertoli cells, derived from 21-day-old Wistar rats, with 5 x 10(-7) M testosterone decreases ornithine decarboxylase (ODC) mRNA levels. In the present study we examined the mechanism of this inhibition. Pretreatment of Sertoli cells for 48 h with 5 x 10(-7) M testosterone decreased ODC mRNA levels 30% at all time points examined. Addition of 25 micrograms/ml cycloheximide (CHX) to the testosterone-pretreated cells resulted in a loss of the testosterone-mediated decrease in ODC mRNA levels by 4 h. Surprisingly, a further 1.8-fold increase in ODC mRNA was observed at 8 h compared to that in untreated cells. Addition of CHX to control cells also resulted in a measurable increase in ODC mRNA levels by 4 h, with a further 1.6-fold increase at 8 h. Identical effects were observed using the protein synthesis inhibitor puromycin (200 micrograms/ml), which has a mechanism of action different from that of CHX. Analysis of the half-life of ODC mRNA after actinomycin-D (5 micrograms/ml) inhibition demonstrated that testosterone did not alter ODC mRNA half-life compared to that in control cells (2.63 vs. 2.55 h). These results demonstrate that the mechanism by which testosterone decreases ODC mRNA levels requires continual protein synthesis, since the effect can be abolished by treating the cells with CHX or puromycin. The data also demonstrate that the testosterone effect is exerted primarily at the transcriptional level, since the half-life of ODC mRNA was not affected by testosterone.

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PubMed1990

Testosterone decreases ornithine decarboxylase messenger RNA levels in primary cultures of rat Sertoli cells.

We have previously reported that testosterone decreased ornithine decarboxylase (ODC) activity in primary cultures of rat Sertoli cells. In this report we examined the mechanism of this reduction. In cells pretreated with testosterone (5 x 10(-7) M) for 48 h before the start of the experiment ODC activity was decreased, on the average, 43% at all time points examined. ODC mRNA levels were also decreased an overall 33%. The testosterone-mediated decrease in ODC activity was first seen 8 h after the addition of testosterone to the cells. Testosterone had no significant affect on the levels of actin or transferrin mRNA. The effect of testosterone was androgen specific. Neither ODC activity nor mRNA was affected by the nonandrogenic steroids progesterone or cortisol. These results suggest that testosterone decreases ODC mRNA in Sertoli cells either through an inhibition of transcription or through a decrease in message stability. Testosterone does not appear to affect ODC mRNA translation, since the percent decreases in ODC activity and mRNA in response to testosterone were essentially equivalent. Regulation of Sertoli cell ODC expression by testosterone may reflect one mechanism by which Sertoli cell function is integrated with surrounding cell types. The Sertoli cell, unlike any other cell, secretes putrescine, the product of ODC catalysis of ornithine. We suggest that the modulation of ODC by testosterone and, hence, the amount of putrescine secreted by the Sertoli cell may be significant in the process of spermatogenesis.

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