Category Archives: Endogenous Insulin

Endogenous Insulin: DISCUSSION(4)

Using the serum-free GC model system, Bicsak et al. showed that endogenously produced IGF-I plays an essential role in FSH-induced E2 and progesterone synthesis by autocrine/paracrine mechanisms. This body of evidence strongly suggests that rat GC secrete IGF-I that acts … Continue reading

Endogenous Insulin: DISCUSSION(3)

Orly et al. have reported that the primary negative effect of A23 occurs at the level of P450 side-chain cleavage and P450 aromatase gene transcription/processing rather than causing decreases in the rate of protein synthesis. They suggested that the PTK … Continue reading

Endogenous Insulin: DISCUSSION(2)

We have demonstrated that nanomolar concentrations of IGFBP-4 or -5 can completely negate the stimulatory effects of a saturating dose of FSH on Inh-a production. A similar result was obtained using a polyclonal anti-IGF-I antibody. Furthermore, we showed that added … Continue reading

Endogenous Insulin: DISCUSSION(1)

These results provide the first experimental evidence to suggest that endogenously produced IGF-I may be a functional requirement for FSH stimulation of Inh-a production. The major observations that underpin this proposal are as follows. First, IGFBP-4, IGFBP-5, and an anti-IGF-I … Continue reading

Endogenous Insulin: RESULTS(3)

Effects of IGFBP-4 and -5 on lnh-а mRNA Steady State Levels Figure 5 shows Northern blot data derived from cells treated alone or together with FSH, IGF-I, and IGFBP-4 and -5. Inh-a mRNA was constitutively present in control (untreated) cells. … Continue reading

Endogenous Insulin: RESULTS(2)

Effects of ICFBP-4 and -5 on FSH-Stimulated Inh-a Production We next investigated the effects of rat IGFBP-4 and -5 on FSH-stimulated Inh-a production. As shown in Figure ЗА, the stimulation of Inh-a by FSH was inhibited in a dose-dependent manner … Continue reading

Endogenous Insulin: RESULTS(1)

Dose-Response and Time-Course Study We first tested the dose-response relationship between FSH, IGF-I, and Inh-a production. Figure 1A shows that FSH stimulated basal levels of 18-kDa Inh-a in cell-free supematants in a dose-dependent manner (ED50 = 0.4 ± 0.1 ng/ml), … Continue reading

Endogenous Insulin: MATERIALS AND METHODS(4)

Northern Blot Analysis After removal of the culture medium for Western blot analysis, total cellular RNA was prepared by using the guanidinium isothiocyanate extraction method . Total RNA (5 |xg) was fractionated on a 1% denaturing agarose gel and transferred … Continue reading

Endogenous Insulin: MATERIALS AND METHODS(3)

Western Blotting Analysis SDS-PAGE was performed under reducing conditions. Conditioned medium was concentrated 10 times using Im-mersible-CX 10 ultrafilters (10 000 molecular weight cutoff). Samples were mixed with denaturing buffer containing 5% 2-mercaptoethanol, heated in a boiling water bath for … Continue reading

Animals Animals were handled in accordance with the NIH Guide for the Care and Use of Laboratory Animals, and the procedures used were approved by the Institutional Animal Care and Use Committee. Immature (23 day old) intact female rats (Wistar; … Continue reading

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