The effects of thyroid hormones and starvation on hepatic mitochondrial nucleic acids of rainbow trout ( Oncorhynchus mykiss)

Twenty four hours after an intraperitoneal injection of thyroxine (T 4; 4.4, 44 ng/g body wt) or triiodothyronine (T 3; 3.3, 33 ng/g body wt), DNA and RNA were significantly reduced in isolated liver mitochondria of rainbow trout. Total liver DNA was increased with the higher doses in both T 4- and T 3-injected specimens while total RNA was significantly reduced with the same doses. Total circulating plasma T 4 was reduced with the injections of T 3 or starvation, and plasma T 3 was increased severalfold with the T 3 injections. Plasma T 4 also increased fivefold after a higher dose of T 4 injection while starvation significantly reduced the concentration, when measured by radioimmunoassay.