We have produced transgenic mouse strains harboring class II major histocompatibility complex or interferon-gamma genes linked to the human insulin promoter. These experiments were designed to investigate the consequences of the expression of immunological effector molecules by nonimmunological cells. In both of these studies we observed the disappearance from the pancreas of the insulin-producing beta cells coinciding with the development of insulin-dependent diabetes mellitus. Transgenic mice expressing both chains of the I-A gene showed progressive atrophy of the islets of Langerhans, whereas mice expressing interferon-gamma suffered an inflammatory destruction of the islets.

The role of inhibin and activin in the initiation of follicular development, growth, and atresia was examined. Human recombinant inhibin (1 microgram) was unilaterally injected into the ovarian intrabursal space of 25-day-old rats. The contralateral ovary served as a control. Recruited growing follicles (350-500 microns) were observed 24 h after injection. The accumulation of follicles was greater in the inhibin-treated ovaries than in contralateral control ovaries. Moreover, the size distribution of the follicles was similar to the distribution of follicles recruited by systemic exogenous PMSG treatment. The effect of inhibin plus PMSG on follicular development was not different from that of PMSG treatment alone. Injection of human recombinant activin (1 microgram) into the ovarian bursa caused follicular atresia. Activin therapy blocked the follicular development caused by PMSG treatment. The effect of inhibin and activin on follicular development was further characterized by measuring the incorporation of [3H]thymidine into dividing cells. Inhibin enhanced follicular thymidine incorporation, while activin decreased granulosa cell proliferation. Furthermore, receptors for inhibin-A (6.4 x 10(3) receptors/cell) and activin-A (2.3 X 10(4) receptors/cell) were identified on granulosa cells. The evidence suggests that inhibin and activin act in a paracrine manner to regulate follicular development, inhibin as a follicular growth signal and activin as an atretagenic signal.

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Hepatocyte growth factor (HGF) is a pluripotent mitogen thought to be involved in liver regeneration. It is synthesized as a single chain promitogen and requires proteolytic processing to a two-chain heterodimeric form for biological activity. The pharmacokinetics and tissue distribution of radioiodinated single chain recombinant human HGF ([125I]rhuHGF) were studied in male Sprague-Dawley rats after an iv bolus dose. Pharmacokinetic parameters were determined from trichloroacetic acid-precipitable radioactivity in serum samples. There was a rapid distribution phase (t1/2 alpha = 3.1 min) and a slower elimination phase (t1/2 beta = 114 min). Tissue distribution was assessed by whole body autoradiography 5, 60, and 1440 min after an iv bolus dose. rhuHGF rapidly distributed to the liver, kidney, adrenal gland, and spleen. The importance of the liver in the rapid clearance and subsequent conversion of single chain pro-rhuHGF to the mitogenically active two-chain form was demonstrated using an isolated rat liver perfusion system. TCA-precipitable radioactivity excreted into the bile (1.0 +/- 0.1%) and released into the venous effluent (38.9 +/- 6.1%) was monitored for 60 min after a portal vein injection. The appearance of radioactivity in both the bile and venous effluent was maximal between 20-35 min. Further characterization of the reduced samples by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and autoradiography revealed that the two-chain form of [125I]rhuHGF was the predominant form after hepatic perfusion. These studies suggest that the liver plays a major role in the rapid clearance and subsequent activation of pro-rhuHGF in vivo.

The tissue distribution of recombinant human inhibin A (rh-inhibin A) and rh-activin A was determined in immature female Sprague Dawley-derived rats after iv administration of radiolabeled proteins. [125I]rh-Inhibin A and [125I]rh-activin A diverge in their distribution to tissues of the immature female rat as examined histologically (whole body autoradiography and thin section analysis) and by computing the percent dose and tissue to blood ratios for individual tissues. [125I]rh-inhibin A accumulated in the spleen, adrenal, bone marrow, and ovary after iv injection. Iodinated rh-inhibin A was also found in the anterior and posterior pituitary. [125I]rh-activin A was found in the ovary and pituitary after iv injection. Little specific binding was found in the spleen or adrenal. The bone marrow accumulated some [125I]rh-activin A which was competed by rh-activin A. The primary route of excretion for radioactivity was the kidney, with the label appearing in the bladder by 10 min after iv injection. Not only do rh-inhibin A and rh-activin A have different pharmacokinetics, but fewer tissues accumulate radioactive rh-activin A than rh-inhibin A.