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The mode of regulation of pyruvate dehydrogenase ec 1.2.4.1 of lactating rat mammary gland effects of starvation and insulin






Biochemical Journal 174(2): 553-562

The mode of regulation of pyruvate dehydrogenase ec 1.2.4.1 of lactating rat mammary gland effects of starvation and insulin

The initial activity of the pyruvate dehydrogenase enzyme [EC 1.2.4.1] complex in whole tissue or mitochondrial extracts of lactating rat mammary glands was greatly decreased by 24 or 48 h starvation of the rats. Injection of insulin and glucose into starved rats 60 min before removal of the glands abolished this difference in initial activities. The total activity of the enzyme complex in such extracts was revealed by incubation in the presence of free Mg2+ and Ca2+ (more than 10 and 0.1 mM, respectively) and a crude preparation of pig heart pyruvate dehydrogenase phosphatase. Starvation did not alter this total activity. The decline in initial activity of the enzyme complex derived from the glands of starved animals probably was due to increased phosphorylation of its .alpha.-subunit by intrinsic pyruvate dehydrogenase kinase. Starvation increased intrinsic pyruvate dehydrogenase kinase activity in both whole tissue and mitochondrial extracts. Insulin injection into starved animals 30 min before removal of lactating mammary glands abolished the increase in pyruvate dehydrogenase kinase activity in whole-tissue extracts. Pyruvate (1 mM) prevented ATP-induced inactivation of the enzyme complex in mitochondrial extracts from glands of fed animals. In similar extracts from starved animals pyruvate was ineffective. Starvation led to a decline in pyruvate dehydrogenase phosphatase activity in mitochondrial extracts, but not in whole-tissue extracts. These changes in activity of the intrinsic kinase and phosphatase of the pyruvate dehydrogenase complex of lactating rat mammary gland are not explicable by current theories of regulation of the complex.


Accession: 006719465



Related references

Baxter, M.A.; Coore, H.G., 1978: The mode of regulation of pyruvate dehydrogenase of lactating rat mammary gland. Effects of starvation and insulin. The 'initial activity' of the pyruvate dehydrogenase (PDH) complex in whole tissue or mitochondrial extracts of lactating rat mammary gland was greatly decreased by 24 or 48 h starvation of the rats. Injection of insulin and glucose into...

Baxter, M.A.; Coore, H.G., 1979: Reduction of mitochondrial pyruvate dehydrogenase phosphatase activity in lactating rat mammary gland following starvation or insulin deprivation. The initial rates of activation of inactivated pyruvate dehydrogenase from lactating rat mammary gland and from pig heart were employed to assay pyruvate dehydrogenase phosphatase activity in mammary gland mitochondrial extracts. 24 h-starvation o...

Baxter, M.A.; Coore, H.G., 1979: Reduction of mitochondrial pyruvate dehydrogenase phosphatase ec 1.6.4.3 activity in lactating rat mammary gland following starvation or insulin deprivation. The initial rates of activation of inactivated pyruvate dehydrogenase from lactating rat mammary gland and from pig heart were employed to assay pyruvate dehydrogenase phosphatase [EC 1.6.4.3] activity in mammary gland mitochondrial extracts. Star...

Baxter, M.A.; Coore, H.G., 1978: Persistent effects of starvation on pyruvate dehydrogenase kinase and phosphatase of lactating rat mammary gland. It is suggested that starvation for 24 h results in a more active pyruvate dehydrogenase kinase in lactating rat mammary gland and probably a less active pyruvate dehydrogenase phosphatase. It is considered unlikely that known effective agents are...

Baxter, M.A.; Coore, H.G., 1978: Persistent effects of starvation on pyruvate dehydrogenase kinase and phosphatase of lactating rat mammary gland [proceedings. Biochemical Society Transactions 6(1): 154-157

Baxter, M.A.; Coore, H.G., 1979: Starvation of lactating rats leads to alterations in the behaviour of pyruvate dehydrogenase kinase which persist in the semi-purified pyruvate dehydrogenase complex of the mammary gland but are partly reversible in vitro. 24-h starvation has been shown to lead to increased steady-state phosphorylation of pyruvate dehydrogenase enzyme complex (PDH) in lactating rat mammary gland in vivo [see preceding abstr. and DSA 41, 2546], this being at least partly due to enhan...

Baxter M.A.; Coore H.G., 1979: Starvation of lactating rats leads to alterations in the behavior of pyruvate dehydrogenase kinase which persist in the semi purified pyruvate dehydrogenase complex of the mammary gland but are partly reversible in vitro. Febs Letters 98(1): 195-198

Baxter, M.A.; Goheer, M.A.; Coore, H.G., 1978: Effects of starvation, diabetes and 2-bromo-alpha-ergocryptine treatment on pyruvate dehydrogenase activity in lactating rat mammary gland. Biochemical Society Transactions 6(5): 968-970

Munday, M.R.; Williamson, D.H., 1981: Role of pyruvate dehydrogenase and insulin in the regulation of lipogenesis in the lactating mammary gland of the rat during the starved-refed transition. Administration of insulin with glucose to starved lactating rats, which activates pyruvate dehydrogenase [M. A. Baxter & H. G. Coore (1978) Biochiem. J. 174, 553-561], restored lipogenesis in mammary gland in vivo to 50% of the value observed...

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