Abstract:
The relationship between photoperiod, plasma
concentration of ionic calcium and the histology of the
prolactin-secreting cells of the rostral pars distalis of
the pituitary gland, the Corpuscles of Stannius and the
Ultimobranchial gland were investigated. Neither the plasma
concentration of ionic calcium nor histologically apparent
prolactin cell activity could be correlated with photoperiod.
Some evidence of a photoperiodic effect on both the Corpuscles
of Stannius and the Ultimobranchial gland was obtained. The
expected reciprocal relationship between the activity of
these glands was not obvious at the histological level
.
Quantitative and qualitative analysis at the light
microscope level revealed, however, that the hormone
prolactin-secreting eta cells of the rostral pars distalis
and the hypocalcin-secreting cells of the Corpuscles of
Stannius may be arranged in a lamellar pattern comprized of
synchronous bands of cells in like-phase of a secretory
cycle consisting of four stages - synthesis, storage, release
and reorganization. Such synchronized cell cycles in these
glands have not heretofore been described in literature.
It is suggested that the maintenance of at least 255? of
the cells in any one phase of the cycle ensures a supply of
the required hormone at all times.
