Harbor Porpoise Thyroids: Histologic Investigations and Potential Interactions With Environmental Factors

Abstract

ABSTRACT:The thyroid plays an important role in development and is of primary importance in metabolism and heat loss for cetaceans, including the harbor porpoise (Phocoena phocoena). Several studies have demonstrated that environmental contaminants can alter various aspects of thyroid function in mammals and may contribute to various histologic changes. The present study completes the data set of a 2006 study by Das et al., by performing histological and immunohistologic investigations on thyroids of 36 harbor porpoises from Belgian and United Kingdom waters. The number and mean diameter of follicles (mm) and the relative proportion of follicular, connective, and vascular tissue (%) were quantified in the thyroid gland of each individual. Interfollicular fibrosis has been observed in these thyroid glands, and the collective findings support the hypothesis of an endocrine disruption of thyroid function through organochlorinated compounds. Our study aimed also to reveal potential relationships between thyroid morphometric data and metal levels (Cd, Fe, Zn, Cu, Se, and Hg) using multivariate statistical analysis. The multiple regressions revealed statistically significant relationships between trace elements (cadmium, selenium, and copper) and thyroid fibrosis. The largely negative relationships are interesting findings but do not support the hypothesis that these elements have an adverse effect on thyroid morphometry. Further research is needed to understand the nature of any relationship between organochlorine and trace element exposure and thyroid gland morphology and function in harbor porpoises.

Transient Receptor Potential C4/5 Like Channel Is Involved in Stretch-Induced Spontaneous Uterine Contraction of Pregnant Rat

“…In addition, TRPM4 [ 12 , 13 , 14 , 15 ] and a long splice variant of TRPM3 [ 11 ] are also activated by hypoosmotic membrane stretch. As for TRPC family, TRPC1 and TRPC6 were reported to be activated by mechanical and hypoosmotic stretch [ 33 , 34 ], which is still in controversy [ 35 , 36 , 37 ]. As for uterine myometrium, there also exists TRPC family in human and rat pregnant myometrium [ 17 , 18 , 38 ].…”

“…As for the mechanistic link between membrane stretch (or cell swelling) and G-protein activation, G protein-coupled receptors (GPCRs) have emerged as a candidate for potential mechanosensors which covert mechanical stimuli to biochemical signals. In fact, various GPCRs such as histamine 1, angiotensin II, acetylcholine and vasopressin receptors are reported to be activated by mechanical stress without the involvement of their ligands [ 37 , 41 ]. For example, it has been reported that in cardinal component of the renin-angiotensin regulatory system, mechanical stress can active the AT1R(angiotensin-II type-1 receptor) independently of angiotensin-II [ 42 ].…”

Thyroid gland lesions in organohalogen contaminated East Greenland polar bears (Ursus maritimus)

“…Bar ¼ 60 mm. depletion (Table 2; Schnitzler 2005;Schnitzler et al 2008;Schumacher et al 1993). In these studies, it was postulated that thyroid colloid depletion and fibrosis in harbor seals (Phoca vitulina), and to a lesser degree in harbor porpoises (Phocoena phocoena), may be linked to high tissue concentrations of PCBs.…”

Small size in the common bottlenose dolphin ­Tursiops truncatus in the eastern Mediterranean: a possible case of Levantine nanism

“…Growth stunting may be caused by the general stress of a high contaminant burden and specifically by thyroid disruptors (Wade et al 2002), even though this has not been directly demonstrated in marine mammals. A correlation between organo -pollutant levels and degree of thyroid gland fibrosis has been demonstrated in eastern North Atlantic harbor porpoises (summarized in Schnitzler et al 2009). Israeli BDs, however, demonstrate total blubber PCB values an order of magnitude lower than those in animals in the western Mediterranean (Shoham-Frider et al 2009), and while possessing relatively high tissue cadmium loads (presumably of natural origin from Sahara sands) (Roditi-Elasar et al 2003), cadmium was shown to be negatively correlated to thyroid gland fibrosis in harbor porpoises (Schnitzler et al 2009).…”