Assessment of thyroid function in adult medaka (Oryzias latipes) and juvenile rainbow trout (Oncorhynchus mykiss) using immunostaining methods

Abstract

The effect of injected bovine TSH on the pattern of anti-T(4) and anti-T(3) immunostaining of the thyroid tissue was examined in rainbow trout (Oncorhynchus mykiss) and medaka (Oryzias latipes) to determine if the previously reported immunostaining of the cytoplasm of thyrocytes is due to the presence of colloid pinocytotic vesicles and is thus indicative of thyroid hormone release. We hypothesized that the number of immunostained thyrocytes should increase following a TSH challenge, and this should parallel other indicators of increased thyroid activity. In medaka, immunostained thyrocytes were only found following the TSH challenge, and were most marked after 24 to 72 hours; the immunostaining was associated with large colloid-filled cytoplasmic vesicles. In trout, the number and staining intensity of immunostained thyrocytes were increased after the TSH challenge; the immunostaining was present throughout the cytoplasm of the thyrocytes. These findings support the working hypothesis that the immunostaining of the thyrocytes is associated with the pinocytosis of thyroglobulin by the thyrocytes in parallel with an increase in release of thyroid hormone, and that this investigational approach provides a reliable indicator of thyroid hormone release activity.

Anatomical and molecular reinvestigation of lamprey endostyle development provides new insight into thyroid gland evolution

“…In order to determine when these thyroid-like cell types become functional, we stained L. fluviatilis embryos and larvae histochemically using antibodies against thyroid hormone (thyroxin, T4). T4 is an iodinated derivative of an amino acid that is presumed to be identical in all vertebrate species, and accordingly the antibody against T4 applied in this study has been successfully used to determine the localisation of T4 in other species including teleosts (Elsalini et al 2003;Raine and Leatherland 2000;Raine et al 2001).…”

Analysis of origin and growth of the thyroid gland in zebrafish

“…To date, only developmental genes have been studied in zebrafish, and differentiation of follicles has been shown using T4 antibody staining. However, T4 is the hormone itself that is released into circulation, and only by means of presumed cross-reaction with intermediate stages of hormone synthesis serves as an indirect marker for thyroid follicles in fish (Raine and Leatherland, 2000;Raine et al, 2001;Wendl et al, 2002). Our analysis reveals that thyroid differentiation occurs even earlier than assumed in previous studies.…”

“…Here, follicle tissue is loosely dispersed along the ventral midline of the pharyngeal mesenchyme, thus, is not encapsulated by connective tissue (Raine and Leatherland, 2000;Raine et al, 2001;Wendl et al, 2002). In zebrafish development, immunostaining of thyroid hormone reveals a first follicle at around 60 hours postfertilization (hpf), when the embryo hatches from the egg shell.…”

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“…In tilapia, Orechromis niloticus, thyroid follicles were reported to be found only in the subpharyngeal region (Geven et al 2007). The thyroid tissue of medeka (Oryzias latipes) comprises two nuclei in the follicles, situated on either side of the ventral aorta (Raine et al 2001). In rainbow trout, the clusters of follicles in the pharyngeal thyroid tissue present adjacent to the ventral aorta (Leatherland 1994;Raine & Leatherland 2000).…”