Abstract
Summary
An acute marked increase in total serum calcium was observed after a single iv injection of lead. The response was prompt, serum calcium rising above 20 mg/dl 60-90 min after doses ≥ 15 mg/kg. The hypercalcemia was due entirely to a rise in the non-dialyzable calcium fraction. In contrast, the ultrafilterable fraction which includes ionic calcium was actually diminished. This explains the absence of an increase in serum calcitonin despite severe hypercalcemia. A slight rise in total plasma proteins also was observed after lead injection but the significance of this observation remains to be determined. These acute effects of lead on calcium homeostasis are apparently different from its chronic effects since we have found, in a separate study, that rats exposed to lead for 1 year developed hyperplasia of C-cells and an increase in the levels of calcitonin in both the blood and the thyroid glands.
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