Induction of the ATP-dependent proteolytic system in guinea pig reticulocyte lysates by triiodothyronine.
The mechanism involved in the decreased numbers of several trans-membrane proteins such as sodium pump sites, sodium-lithium countertransport, sodium potassium cotransport proteins, proteins mediating the passive efflux of sodium and insulin receptors in erythrocytes from patients with hyperthyroidism is not known. The ATP-dependent proteolytic system which is involved in the loss of trans-membrane proteins during the maturation of the reticulocyte may be involved in the accelerated loss of these membrane proteins. Therefore, the effect of thyroid hormones on the ATP-dependent proteolytic activity of reticulocyte lysates was examined in this study. Reticulocytosis was induced in 14 guinea pigs by phenylhydrazine hydrochloride injections for 5 consecutive days followed by 2 days of rest. T3 (10 micrograms/100 g body weight) was injected into 7 animals on day 4 and day 6. Reticulocyte-rich blood was withdrawn on day 8. Oxygen consumption determined 24 hours after injection of T3 was 25% higher (p less than 0.01) and T3 treated animals had a 2.5 fold higher (p less than 0.01) weight loss than control animals. The ATP-dependent proteolytic activity measured in reticulocyte lysates using 125I labelled lysozyme was 3.6 fold higher in the T3 than in the control group of guinea pigs (p less than 0.01). We conclude that thyroid hormones induce the ATP-dependent proteolytic activity of reticulocyte lysates which may be responsible for the reduced number of several trans-membrane proteins found in erythrocytes from patients with hyperthyroidism.
Arumanayagam
M
M
Department of Chemical Pathology, Chinese University of Hong Kong, Shatin, New Territories.
Swaminathan
R
R
D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D001772:Blood Cell Count; D001835:Body Weight; D006168:Guinea Pigs; D008565:Membrane Proteins / Q000378:metabolism*; D009113:Muramidase / Q000378:metabolism; D010101:Oxygen Consumption; D012156:Reticulocytes / Q000187:drug effects* / Q000378:metabolism; D014284:Triiodothyronine / Q000494:pharmacology*
D008565:Membrane Proteins; D014284:Triiodothyronine; D000255:Adenosine Triphosphate; D009113:Muramidase