Summary
To determine the localization of T4 5′-monodeiodinase activity in rabbit and rat nephron segments, the formation of tri-iodothyronine
(T3 ) from thyroxine (T4) was measured in kidney homogenate and in isolated nephron segments obtained by the
microdissection method. In order of decreasing activity, homogenates of rabbit renal
cortex, outer medulla and inner medulla were capable of converting T4 to T3. In the isolated nephron segments of the rabbit cortex, the activities were noted
in both proximal convoluted and proximal straight tubules. On the other hand, the
activities were not detected in segments including the cortical thick ascending limb
of Henle's loop, the distal convoluted tubule, the connecting tubule, and the cortical
collecting tubule. It is concluded that both the convoluted and the straight tubules
are the sites of T3 production in the kidney.
Key-Words:
Thyroxine
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3,5,3′-Triiodothyronine
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Renal Tubules
