394
D. HAROLD COPP
V. SUMMARY
The ultimobranchial glands are now recognized as the source of the
calcium-regulating hormone calcitonin, which in mammals controls hypercalcemia and lowers plasma calcium by inhibiting bone resorption. The
ultimobranchials are well-developed functioning glands in chimaeroids,
elasmobranchs, and teleosts and contain high concentrations of calcitonin.
Indeed the salmon hormone appears to be much more potent than that
extracted from hog thyroid. Because the field is still very new, there is
little data available to indicate its function in fishes. Porcine calcitonin
was reported to lower plasma calcium in the eel, Anguilla unguillu, and in
the catfish, Zctulumrs meh-both teleosts with cellular bone. No effect
was observed in Fundulus heteroclitus which has acellular bone.
While it seems very probable that the ultimobranchial gland in fishes
is involved in controlling hypercalcemia as is the case in terrestrial vertebrates, the exact mechanisms are not known. Certainly in cartilaginous
fishes (chimaeroids and elasmobranchs) and in teleosts with acellular
bone, it is unlikely that its action is primarily on the skeleton. It seems
more likely that it acts to facilitate calcium transport across cell membranes particularly in critical barriers such as the gills, gut, or kidney.
This should provide a fruitful field for investigation by fish physiologists.
ACKNOWLEDGMENTS
The author would like to express his deep appreciation to Dr. William A. Webber
of the Department of Anatomy, University of British Columbia for preparing the light
and electron micrographs of fish ultimobranchials which are included in this chapter.
Certain of the experimental work reported received support from the Medical Research Council and the Associate Committee on Dental Research of the National
Research Council of Canada. Mrs. Gale Butchart assisted with the preparation of the
manuscript.
REFERENCES
Aliopoulios, M. A., Goldhaber, P., and Munson, P. L. (1968). Thyrocalcitonin inhibition of bone resorption induced by parathyroid hormone in tissue culture. Science
151,330451.
Anast, C. S. (1986). Thyrocalcitonin-a review. Clin. Orthopaed. 47, 179-187.
Amaud, C. D., Littledike, T., Tsao, H. S., and Kaplan, F. L. (19eS). Radioimmunoassay of calcitonin: A preliminary report. Mayo C h . Proc. 45, 496302.
Baber, E. C. ( 1876). Contributions to the minute anatomy of the thyroid gland of the
dog. Proc. Roy. SOC. 24,240-241.
Bell, P. H., Barg, W. F., Jr., Colucci, D. F., Davies, M. V., Dziokowski, C., Englert,
M. E., Heyder, E., Paul, R., and Snedeker, E. H. (1988). Purification and
structure of porcine calcitonin-1. J. Am. Chem. SOC. 90, 2704-2706.
D. HAROLD COPP
V. SUMMARY
The ultimobranchial glands are now recognized as the source of the
calcium-regulating hormone calcitonin, which in mammals controls hypercalcemia and lowers plasma calcium by inhibiting bone resorption. The
ultimobranchials are well-developed functioning glands in chimaeroids,
elasmobranchs, and teleosts and contain high concentrations of calcitonin.
Indeed the salmon hormone appears to be much more potent than that
extracted from hog thyroid. Because the field is still very new, there is
little data available to indicate its function in fishes. Porcine calcitonin
was reported to lower plasma calcium in the eel, Anguilla unguillu, and in
the catfish, Zctulumrs meh-both teleosts with cellular bone. No effect
was observed in Fundulus heteroclitus which has acellular bone.
While it seems very probable that the ultimobranchial gland in fishes
is involved in controlling hypercalcemia as is the case in terrestrial vertebrates, the exact mechanisms are not known. Certainly in cartilaginous
fishes (chimaeroids and elasmobranchs) and in teleosts with acellular
bone, it is unlikely that its action is primarily on the skeleton. It seems
more likely that it acts to facilitate calcium transport across cell membranes particularly in critical barriers such as the gills, gut, or kidney.
This should provide a fruitful field for investigation by fish physiologists.
ACKNOWLEDGMENTS
The author would like to express his deep appreciation to Dr. William A. Webber
of the Department of Anatomy, University of British Columbia for preparing the light
and electron micrographs of fish ultimobranchials which are included in this chapter.
Certain of the experimental work reported received support from the Medical Research Council and the Associate Committee on Dental Research of the National
Research Council of Canada. Mrs. Gale Butchart assisted with the preparation of the
manuscript.
REFERENCES
Aliopoulios, M. A., Goldhaber, P., and Munson, P. L. (1968). Thyrocalcitonin inhibition of bone resorption induced by parathyroid hormone in tissue culture. Science
151,330451.
Anast, C. S. (1986). Thyrocalcitonin-a review. Clin. Orthopaed. 47, 179-187.
Amaud, C. D., Littledike, T., Tsao, H. S., and Kaplan, F. L. (19eS). Radioimmunoassay of calcitonin: A preliminary report. Mayo C h . Proc. 45, 496302.
Baber, E. C. ( 1876). Contributions to the minute anatomy of the thyroid gland of the
dog. Proc. Roy. SOC. 24,240-241.
Bell, P. H., Barg, W. F., Jr., Colucci, D. F., Davies, M. V., Dziokowski, C., Englert,
M. E., Heyder, E., Paul, R., and Snedeker, E. H. (1988). Purification and
structure of porcine calcitonin-1. J. Am. Chem. SOC. 90, 2704-2706.