In the present study, we have measured protein kinase C (PKC) specific activities and total diacylglycerol (DAG) level in the aorta and heart of rats, which showed that after 2 weeks of streptozotocin (STZ)-induced diabetes, membranous PKC specific activity and total DAG content were increased significantly by 88% and 40% in the aorta and by 21% and 72% in the heart, respectively. Hyperglycemia was identified as being a causal factor since elevated glucose levels increased DAG levels in cultured aortic endothelial and smooth muscle cells. Analysis by immunoblotting revealed that only a and 1II PKC isoenzymes are detected in these two tissues and vascular cells among those studied. In STZ-induced diabetic rats, PII isoenzyme is preferentially increased in both aorta and heart, whereas PKC a did not change significantly. The increases in membranous PKC specific activity and DAG level are observed in both spontaneous diabetes-prone diabetic BB rats as well as in STZ-induced diabetic BB and SpragueDawley rats, which persisted for up to 5 weeks. After 2 weeks of diabetes without treatment, the normalization of blood glucose levels for up to 3 weeks with islet cell transplants in STZ-induced diabetic BB rats reversed the biochemical changes only in the heart, but not in the aorta. These results suggest that PKC activity and DAG level may be persistently activated in the macrovascular tissues from diabetic animals and indicate a possible role for these biochemical parameters in the development of diabetic chronic vascular complications.Cardiovascular disease is the leading cause of mortality and morbidity in diabetic patients (1, 2). Pathological studies have shown an increased rate of atherosclerotic lesions (1, 2); cardiac muscle cell dysfunction has also been reported (3). Hyperglycemia appears to be one of the many possible risk factors in diabetic patients (4, 5). Several hypotheses have been proposed to explain the adverse effects of hyperglycemia (6-8). We have reported that protein kinase C (PKC) was activated in the retina of diabetic rats as well as in cultured vascular cells exposed to elevated levels of glucose (9). The mechanism of PKC activation may be due to increased production of diacylglycerol (DAG) in retinal microvessels due to high glucose levels (9). Other investigators have reported that hyperglycemia and glucose can activate PKC in the microvessels of renal glomeruli (10) and granulation tissues (11) due to an increase in production of DAG.The alteration of PKC by diabetes and glucose is interesting since PKC activity has been shown to modulate smooth muscle growth (12) and contraction (13,14), endothelial cell permeability (15), expression of signal transduction of hormones and growth factors (16, 17), and cardiomyocyte contractility (18). All of these functions have been reported to be abnormal in diabetic animals or patients. In the present study, we have determined the changes of PKC specific activities and its isoforms as well as DAG levels in the aorta and heart of diabetic rats. I...

To investigate the role of RT6+ T cells in the pathogenesis of diabetes in BB/W rats, we treated animals from the diabetes-resistant (DR) subline with anti-RT6.1 lymphocytotoxic mAb. This depleted greater than 95% of peripheral RT6+ T cells but did not substantially reduce levels of circulating T cells or the in vitro response of spleen cells to mitogen. Treatment of 30-d-old DR BB/W rats in this way: induced insulitis and diabetes, rendered nondiabetic RT6-depleted DR rats susceptible to the adoptive transfer of diabetes by spleen cells from acutely diabetic BB/W rats, and yielded DR spleen cell populations capable of the adoptive transfer of diabetes to diabetes-prone (DP) or DR recipients. Treatment of DR rats beginning at 60 d of age failed to produce these effects. These results suggest that both susceptibility and resistance to diabetes in the BB/W rat are in part regulated by the RT6+ T cell subset and provide evidence for the importance of regulatory T lymphocytes in the pathogenesis of autoimmunity and diabetes in BB/W rats.

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We describe the induction of autoimmune diabetes, insulitis, and thyroiditis in athymic rats following ujections of major histocompatibiity complex compatible spleen cells. Lymphocytes with these capabilities were found in normal rats ofthe YOS, WAG, PVG, and diabetes-resistant BB strains, and in diabetes-prone BB rats. Adoptive transfer was facilitated by prior in vivo depletion of RT6.1+ regulatory T cells and in vitro mitogen activation of donor spleen cells. By RT6 depleting diabetes-resistant donors and nsing nude recipients, transfer of diabetes and thyroiditis was accomplished by using fresh, unstimulated spleen cells. The data suggest that organ-specific autoreactive cells may be present to various degrees but suppressed to a variable extent in many rat strains. The equilibrium between autoreactive and regulatory cells appears to determine the expression of autoimmunity.Clonal deletion of autoreactive lymphocytes during repertoire development and active suppression of autoreactive cells in peripheral tissues contribute to the prevention of autoimmune diseases (1). In mice, T-lymphocyte populations are deleted in the thymus following interaction with a major histocompatibility complex (MHC) class II (I-E) molecule (2). Nonobese diabetic mice do not express I-E and develop autoimmune diabetes (3). These mice harbor T-cell populations normally deleted in I-E-expressing strains (4). In B6AF1 mice, neonatal thymectomy induces organ-specific autoimmunity (5). Thymectomy earlier or later is ineffective, suggesting that a sequence ofintrathymic events culminates in an immunological definition of self.Evidence for suppression of autoreactive T cells in peripheral tissues is also accumulating. Transplantation of Lyt-1-depleted spleen cells from nu/+ mice (6) or thymuses from cyclosporin-treated nu/+ mice (7) into nu/nu recipients results in autoimmune endocrinopathy. This can be prevented by cotransplantation of a nu/+ thymus or unfrictionated spleen cells together with the cyclosporin-treated thymus.An imbalance between autoreactive and regulatory (RT6+) cells may in part determine the expression of BB rat autoimmunity (8). Diabetes-prone (DP) BB rats are lymphopenic and deficient in T cells that express the RT6 alloantigen (9). They spontaneously develop insulitis, hyperglycemia, and thyroiditis (8,10 ITo whom reprint requests should be addressed. 7618The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.Proc. Natl. Acad. Sci. USA 87 (1990) 7619 isolated splenocytes were injected into recipients (108 cells in 0.5 ml per rat).Flow Microfluorimetry. To determine the number of native T cells present in athymic rats and to assay for chimerism in adoptive recipients, lymph node cell suspensions were labeled with 0X19 mouse anti-rat CD5 (pan-T cell) monoclonal antibody (mAb), with the rat anti-RT6.1 mAb DS4.23, or with the rat anti-RT6.2 mAb 6A5 (9). Cell...