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Endogenous production of specific antibodies does not decrease hypocalcemic response to calcitonin in young rabbits
J Y Reginster1, M Azria, S Gaspar
1Bone Metabolism Unit, University of Liege, Policliniques Universitaires Lucien Brull, Belgium.
Abstract:
In order to evaluate the potential inhibition of the acute anti-osteoclastic activity of salmon calcitonin (SCT) by specific antibodies (Ab), we compared the SCT-induced hypocalcemic effect in young male rabbits with significant titers of high affinity Ab and in matched animals without Ab. Immunization of rabbits was performed by repetitive s.c. injections of SCT and Freund adjuvant. Ab were present in four-fifths of SCT-treated rabbits (Ab+). Their titer varied from 0.8 x 10(-9) to 30 x 10(-9) M/liter and their constant of affinity from 0.97 x 10(9) to 4.2 x 10(9) L/M. Intravenous injection of 1 IU/kg SCT to Ab+ rabbits induced a significant decrease (P less than 0.01) of ionized serum calcium (Ca2+) after 30 minutes (mean +/- SD: -9 +/- 0.6%) and until the 240th minute of the test (-16.7 +/- 4.7%), with a maximum after 120 minutes (-22.6 +/- 2%). This was not significantly different from the hypocalcemic effect measured after the same procedure performed in matched animals without Ab (Ab-): significant decrease in Ca2+ (P less than 0.01) after 30 minutes (-8.2 +/- 2.2%), maximal after 150 minutes (-23.2 +/- 4.9%), and lasting until 210 minutes (-14.5 +/- 3.7%). We conclude that, in the particular model of the male young rabbit, specific anti-SCT Ab do not block or reduce the acute anti-osteoclastic activity of SCT.
Insights
Specific antibodies against salmon calcitonin (SCT) did not inhibit its acute anti-osteoclastic activity in young male rabbits. The hypocalcemic effect of SCT remained similar in rabbits with high-affinity antibodies and those without.
Area of Science:
- Endocrinology
- Immunology
- Pharmacology
Background:
- Salmon calcitonin (SCT) is known for its acute anti-osteoclastic activity.
- The potential for specific antibodies (Ab) to inhibit SCT's therapeutic effects is a relevant consideration.
Purpose of the Study:
- To evaluate whether specific antibodies against salmon calcitonin (SCT) can inhibit its acute anti-osteoclastic activity.
- To compare the hypocalcemic effect of SCT in rabbits with and without high-affinity anti-SCT antibodies.
Main Methods:
- Young male rabbits were immunized to develop specific anti-SCT antibodies (Ab+).
- A control group of rabbits without antibodies (Ab-) was established.
- The hypocalcemic effect of intravenous SCT injection (1 IU/kg) was measured by monitoring ionized serum calcium (Ca2+) levels over time in both groups.
Main Results:
- Rabbits with anti-SCT antibodies (Ab+) showed a significant decrease in Ca2+ post-SCT injection, comparable to rabbits without antibodies (Ab-).
- The timing and magnitude of the maximal hypocalcemic effect were not significantly different between the Ab+ and Ab- groups.
- Specific anti-SCT antibodies did not block or reduce the acute hypocalcemic (anti-osteoclastic) activity of SCT in this rabbit model.
Conclusions:
- In young male rabbits, specific anti-SCT antibodies do not interfere with the acute anti-osteoclastic effects of SCT.
- The study suggests that antibody formation against SCT may not be a significant barrier to its short-term therapeutic efficacy in this model.