Effects of thyroid hormones on heart and kidney functions.
Thyroid hormones affect the functions of several organs including the heart and kidney. Using isolated left papillary muscles we have investigated the action of thyroid hormones on the mechanical and electrical properties of the heart. We found that pure hypothyroidism causes a depression in contractile and electrical parameters, but we noticed that superimposed hypoparathyroidism accounts for the marked prolongation in contractile kinetics and action potential duration. At kidney level we have shown that thyroid hormones affect proximal tubular sodium transport and this effect is only partially mediated by the action of thyroid hormones on Na-K-ATPase activity. Using the micropuncture technique, we hypothesized that the early effect of thyroid hormone action is on the potassium permeability of proximal tubular cell membrane. This latter effect would explain the increase in isotonic fluid reabsorption through an increase in the driving force for sodium. Finally, hypothyroid patients have a decrease in glomerular filtration rate and renal plasma flow that are completely reversed by thyroxine administration. On the other hand, hyperthyroid subjects exhibit a significant increase in both parameters.
Capasso
G
G
Chair of Nephrology, Second University of Naples, Napoli, Italy. gcapasso@unina.it
De Tommaso
G
G
Pica
A
A
Anastasio
P
P
Capasso
J
J
Kinne
R
R
De Santo
N G
NG
D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D005919:Glomerular Filtration Rate / Q000187:drug effects / Q000502:physiology; D006321:Heart / Q000187:drug effects* / Q000502:physiology; D006801:Humans; D006980:Hyperthyroidism / Q000188:drug therapy / Q000503:physiopathology; D007037:Hypothyroidism / Q000188:drug therapy / Q000503:physiopathology; D007668:Kidney / Q000187:drug effects* / Q000502:physiology; D007687:Kidney Tubules, Proximal / Q000187:drug effects / Q000378:metabolism; D008297:Male; D008871:Microvilli / Q000378:metabolism; D010210:Papillary Muscles / Q000187:drug effects; D011677:Punctures; D051381:Rats; D017208:Rats, Wistar; D012964:Sodium / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D013974:Thyroxine / Q000494:pharmacology* / Q000627:therapeutic use; D014284:Triiodothyronine / Q000494:pharmacology* / Q000627:therapeutic use; D016277:Ventricular Function, Left / Q000187:drug effects
D014284:Triiodothyronine; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D013974:Thyroxine