Remodeling of turkey adrenal steroidogenic tissue induced by dietary protein restriction: The potential role of cell death

The present study focused on the cellular remodeling of steroidogenic tissu e in the domestic turkey (Meleagris gallopavo) adrenal gland in response to dietary protein restriction stress. Immature male turkeys (1 week old) wer e fed isocaloric synthetic diets containing either 28% (control) or 8% (res triction) soy protein for 4 weeks. Adrenal glands were processed for the is olation of density-separable, visibly distinct adrenal steroidogenic cell s ubpopulations: three low-density subpopulations [LDAC-1 (rho = 1.0350 -1.04 90 g/ml), LDAC-2 (rho = 1.0490 -1.0570 g/ml), and LDAC-3 (rho = 1.0570-1.05 85 g/ml)] and one high-density subpopulation [HDAC (rho = 1.0590-1.0720 g/m l)]. Dietary protein restriction increased the proportion of LDAC-3 and HDA C by 98 and 350%, respectively, and decreased LDAC-2 by 46%. LDAC-1 also sh owed signs of proportional decrement. To determine the role of cell death i n this process, the potential for apoptosis was assessed in adrenal tissue and isolated adrenal steroidogenic cells using short-term culture followed by analysis of oligonucleosome formation. Basal, culture-triggered oligonuc leosome formation of tissue and cells derived from protein-restricted birds was 80% greater than that of tissue and cells derived from control birds. This differential in apoptotic potential persisted with a variety of treatm ents, in vitro. Apoptotic potential was suppressed by human adrenocorticotr opin and enhanced by angiotensin II (Ang II). The proapoptotic effect of An g II (100 nM) with adrenal fragments was inhibited by the Ang II receptor a ntagonist [Sar(1), Iles(8)]ang II (10 mu M) to below basal values (by about 60%), but the inhibition was surmountable by high concentrations (10 and 1 00 mu M) of Ang II. The antagonist also attenuated basal, culture-triggered DNA fragmentation of tissue and cells, suggesting that at least part of th e basal DNA fragmentation was due to intrinsically generated Ang II. Differ ences in apoptotic potential were also apparent with cell subpopulations. C ompared to control subpopulations, protein restriction enhanced basal oligo nucleosome formation in LDAC-1 and -2 by 38 and 122%, respectively, and red uced it in LDAC3 and HDAC by 53 and 70%, respectively. These data suggest a role for apoptotic cell death in the remodeling of turkey adrenal steroido genic tissue induced by dietary protein restriction. In addition, other dat a suggest that Ang II is an important regulator of adrenal steroidogenic ce ll turnover in the avian adrenal gland. (C) 2000 Academic Press.