Tissue chromium exchange in the rat.

This study of chromium (Cr) exchange in the rat combined measurements of 51Cr distribution and tissue Cr content to permit an assessment of tissue Cr exchange under control conditions and during varied Cr intakes. Liver Cr was found to be 50 to 100% exchangeable whereas pancreas Cr was only 34% exchangeable. In kidney, the specific activity of 51Cr exceeded that of serum by more than 100%, indicating a complex type of exchange involving both a rapidly exchanging Cr pool and an "inner" Cr pool with "sink-like" characteristics. Chromium deprivation of moderate degree reduced serum Cr and tissue exchangeable Cr pools but did not change total tissue Cr, 51Cr distribution, or glucose tolerance. Chromium supplementation and Cr overload increased serum Cr and total, exchangeable, and nonexchangeable tissue Cr pools but did not alter 51Cr distribution. These results indicate that the merging of tracer techniques with tissue Cr analyses yields a more complete view of Cr exchange than 51Cr distribution alone. The data support the hypothesis that specific transport characteristics exist in tissues that may regulate the biological role of Cr.

Radiochromium distribution in thyroid and parathyroid deficiency.

Body retention and tissue distribution of a 51chromium (Cr) tracer were studied in thyroparathyroidectomized (TPTX) rats and in TPTX rats after replacement with thyroxin, calcitonin, or parathyroid hormone. A tracer dose containing 1 ng Cr or less and 0.5 to 0.7 muCi of high specific activity 51Cr (Cr III) was injected intravenously in control, TPTX, and TPTX animals receiving hormone replacement. Three days later, the 51Cr content of the serum and various tissues was determined and the data were expressed as percent dose per milliliter or gram and as tissue: serum 51Cr ratios. TPTX resulted in a significant increase in total body 51Cr retention and 40 to 240% increases in serum and tissue 51Cr levels. Tissue:serum 51Cr ratios were uniformly depressed. Replacement with thyroxin completely or partially reversed these changes in all tissues studied except bone. Calcitonin and parathyroid hormone had no consistent effect on body, serum, or tissue 51Cr levels. These data, indicating that 51Cr distribution is influenced by thyroid hormone activity but not by calcitonin or parathyroid hormone, are compatible with the hypothesis that thyroid hormone controls cellular Cr transport.

Radiochromium distribution in hypophysectomized and adrenalectomized rats.

The effects of hypophyseal and adrenal ablation (HYPOX, ADX) on trivalent radiochromium (51Cr) distribution and of GH and T4 replacement in HYPOX rats were determined. Hypophysectomy increased body retention of 51Cr by 20--35%, and hormonal replacement restored body retention to normal. Serum 51Cr was increased 300--800%, resulting in depressed tissue to serum 51Cr ratios. GH replacement partially restored the 51Cr distribution abnormalities in HYPOX rats to normal. The combination of T4 with GH enhanced the restoration of normal 51Cr distribution, and tissue to serum 51Cr ratios returned to baseline levels. ADX had no effect on body retention of 51Cr but had a small effect on increases in serum and tissue 51Cr levels. As a result, tissue to serum 51Cr ratios did not change. These data indicate that in the HYPOX state there is a marked disturbance in Cr metabolism which is due to deficiencies of both GH and T4. Whether or not adrenal hormones are envolved in 51Cr distribution will require further study.

Automated analysis of hydroxyproline with elimination of non-specific reacting substances.

A modified urinary hydroxyproline method is presented which utilizes an automated technique, Technicon instrumentation and Ehrlich's reagent. Acid hydrolysates are neutralized automatically. Non-specific reacting substances are determined simultaneously with each sample and subtracted as a blank. This method has been found to be superior to the use of charcoal-resin as an absorbent. After blank correction, the mean hydroxyproline excretion of normal and osteoporotic patients are similar. In all groups studied, including Paget's disease, the blanks reresent a significant fraction of total reacting substances and show wide variation between samples. Multiple samples from patients over a two year period show little variation in hydroxyproline excretion when corrected for non-specific reacting substances.