Thyroid hormones modulate zinc transport activity of rat intestinal and renal brush-border membrane.
Thyroid hormone status influences the Zn2+ and metallothionein levels in intestine, liver, and kidney. To evaluate the impact of thyroid hormones on Zn2+ metabolism, Zn2+ uptake studies were carried out in intestinal and renal brush-border membrane vesicles (BBMV). Steady-state Zn2+ transport in intestinal and renal cortical BBMV was increased in hyperthyroid (Hyper-T) rats and decreased in the hypothyroid (Hypo-T) rats relative to euthyroid (Eu-T) rats. In both the intestinal and renal BBMV, Hyper-T rats showed a significant increase in maximal velocity compared with Eu-T and Hypo-T rats. Apparent Michaelis constant was unaltered in intestinal and renal BBMV prepared from the three groups. Fluorescence anisotropy of diphenyl hexatriene was decreased significantly in intestinal and renal brush-border membrane (BBM) isolated from Hyper-T rats compared with Hypo-T and Eu-T rats. A significant reduction in the microviscosity and transition temperature for Zn2+ uptake in intestinal and renal BBM from Hyper-T rats is in accordance with the increased fluidity of these BBMs. These findings suggest that the increased rate of Zn2+ transport in response to thyroid hormone status could be associated with either an increase in the number of Zn2+ transporters or an increase in the active transporters due to alteration in the membrane fluidity. Thus the thyroid hormone-mediated change in membrane fluidity might play an important role in modulating Zn2+ transport activity of intestinal and renal BBM.
Prasad
R
R
Department of Biochemistry, Postgraduate Institute of Medical Education and Research, Chandigarh-160012, India. medinst@pgi.chd.nic.in
Kumar
V
V
Kumar
R
R
Singh
K P
KP
D000818:Animals; D001692:Biological Transport; D003404:Creatinine / Q000097:blood; D005919:Glomerular Filtration Rate; D006980:Hyperthyroidism / Q000378:metabolism; D007037:Hypothyroidism / Q000378:metabolism; D007413:Intestinal Mucosa / Q000378:metabolism*; D007672:Kidney Cortex / Q000378:metabolism*; D007700:Kinetics; D008099:Liver / Q000378:metabolism; D008297:Male; D008871:Microvilli / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D013961:Thyroid Gland / Q000502:physiology; D013963:Thyroid Hormones / Q000502:physiology*; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood; D015032:Zinc / Q000378:metabolism*
D013963:Thyroid Hormones; D014284:Triiodothyronine; D003404:Creatinine; D015032:Zinc; D013974:Thyroxine