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Dialysable and non‐dialysable hydroxyproline in the rat's urine: age related and diurnal variations
Author(s) -
Gaggi Renato,
Gianni Anna Maria,
Montanaro Nicola
Publication year - 1982
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1982.sp014173
Subject(s) - hydroxyproline , endocrinology , medicine , calcitonin , excretion , resorption , chemistry , urinary system , circadian rhythm , parathyroid hormone , hormone , biology , calcium
1. Urinary dialysable and non‐dialysable hydroxyproline, which are considered good indices of bone resorption and neoformation respectively, were determined in rats under conditions that modify skeleton metabolism, such as body growth and parathyroid or calcitonin administration. It was also investigated whether dialysable and non‐dialysable hydroxyproline excretions showed significant circadian fluctuations in rats of different ages. 2. Dialysable hydroxyproline excretion sharply decreased from the first to the fifth months of age and underwent further gradual reduction up to the fourteenth month of life. Non‐dialysable hydroxyproline excretion followed a smoother decrease up to the fifth month, then remained constant. Urinary excretion of non‐dialysable hydroxyproline expressed as a percentage of the total hydroxyprolinuria (n.d.%) slowly increased with advancing rat age. 3. In 2‐, 4‐ and 6‐month old rats, dialysable hydroxyproline excretion showed significant circadian fluctuations with minima and maxima at the end of the dark and light fraction of the cycle respectively. Daily fluctuations were greater in young and adult rats (50‐65% of the respective average levels) than in 4‐month old rats (25%). Non‐dialysable hydroxyproline excretion followed similar but less pronounced patterns. Significant circadian fluctuations of n.d.% were detectable only in 2‐ and 4‐month old rats, with peaks at 04.00‐05.00 hr, thus indicating that the bone formation/resorption ratio increased in the nocturnal fraction of the cycle. 4. Young rats administered with calcitonin exhibited reduced levels of urinary dialysable but not of non‐dialysable hydroxyproline when the hormone was given at 13.30 hr. No changes were observed when calcitonin was injected at 19.30 hr. On the contrary, both diurnal and nocturnal parathyroid hormone administration to young rats caused increased levels of dialysable and non‐dialysable hydroxyproline of the same magnitude.