Abstract
We studied the variation in plasma Sm-C in unrestrained, cannulated rats. Six rats were sampled every 15 min for 6 hr, and 5 rats were sampled every 2 hr for 36 hr. Plasma was assayed for Sm-C (RIA) before and after acid-ethanol extraction (AE), and for growth hormone (GH). AE increased the immunoreactivity of Sm-C in heparinized rat plasma and in freshly-collected serum 3-fold AE had no effect on serum stored at −20° C. >4 wks, which had comparable potency to AE serum and AE plasma. In rats sampled every 15 min, GH showed high amplitude, light entrained pulses every 3.3 ± 0.15 (SEM) hr. By visual inspection, there were no pulses of Sm-C. We further analyzed the data with 2 computer algorithms designed to detect hormone pulses. Of the 5 Sm-C pulses identified by both programs in unextracted plasma, only 1 was also identified in the corresponding AE plasma. When both pulse detection methods were applied to the data from both unextracted and AE plasma from all 6 rats, no pulses were identified in 10 of the 24 series of measurements. In 19 identical dilutions of a single serum sample, one program identified 2 “pulses,” and the other, none. In rats sampled every 2 hr for 36 hr, there was no episodic fluctuation of Sm-C. Thus, there is little evidence for episodic release of Sm-C into blood, either as pulsations entrained to light or to feeding cycles. Sm-C measurements made on single blood samples from normal animals reliably reflect Sm-C concentrations over the course of 24 hr.
Article PDF
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Donaghue, K., Badger, T., Millard, W. et al. ABSENCE OF ULTRADIAN RHYTHM OR DIURNAL VARIATION IN CIRCULATING SOMATOMEDIN-C (Sm-C) IN RATS. Pediatr Res 21 (Suppl 4), 246 (1987). https://doi.org/10.1203/00006450-198704010-00475
Issue Date:
DOI: https://doi.org/10.1203/00006450-198704010-00475