Marie Baudyšová

Low content of mitochondrial ATPase in brown adipose tissue is the result of post-transcriptional regulation

The mRNA levels of ATPase β, ATPase 6, cytochrome oxidase (COX) VIb and COX I subunits were found to be 2.4–13.8‐fold higher in brown adipose tissue (BAT) than in heart, skeletal muscle, brain and liver of mice. The comparison with tissue contents of ATPase and COX revealed that the selective, 5–11‐fold reduction of ATPase in BAT is not caused by decreased transcription of ATPase genes. Likewise, the ATPase β and COX VIb mRNA levels in cultured brown adipocytes were also not influenced by norepinephrine, which activated the expression of the UCP gene by two orders of magnitude. The results indicate that the biosynthesis of mitochondrial ATPase in BAT is post‐transcriptionally regulated.

Control of Synthesis of Uncoupling Protein and ATPase in Animal and Human Brown Adipose Tissue

Biogenesis of two energy-converting and adenine nucleotide-binding proteins of brown adipose tissue mitochondria — the uncoupling protein (UCP) and ATP synthase (ATPase) has been investigated in situ and in cell cultures. Highly differentiated synthesis of these proteins was found to result from distinct regulatory events. Tissue-specific, heat-producing UCP is transcriptionally regulated by a cAMP-dependent and triiodothyronine-dependent mechanism which is operated through β3 adrenoreceptors and involves de-novo synthesis of intracellular iodothyronine 5′-deiodinase. UCP gene can be rapidly turned on and the rate of its expression can differ by several orders of magnitude. In contrast, the synthesis of ATPase which is highly depressed in brown adipose tissue appears to be posttranscriptionally controled and does not exhibit apparent sensitivity to catecholamines.

Effect of Age on Kidney Hyperplasia in the Rat during Cold Acclimation

In adult rats acclimated to 5 degrees C, the kidney weight increases with the length of the exposure. Kidney cells of younger rats survive explantation better than the cells of control rats of the same age. Kidney cells of older rats after cold acclimation and after unilateral nephrectomy have a lower vitality in vitro than corresponding control cells. Unilateral nephrectomy performed in rats aged 3 and 6 months, exposed previously to low temperature, leads to a better survival of explanted kidney cells than nephrectomy or cold only. Old rats do not survive exposure to 5 degrees C for more than 18 hr.