Toxicology International (Formerly Indian Journal of Toxicology)

Saroj Kaler , Pushpa Dhar , Arnab Bhattacharya , Raj D. Mehra

Abstract

The effects of arsenic exposure during rapid brain growth period (RBGP) (postnatal period 4-11) on pyramidal neurons of cornu ammonis (specifically CA1 and CA3 regions) and granule cells of dentate gyrus (DG) of rat hippocampus were studied. Wistar rat pups, subdivided into the control (group I) and the experimental groups (group II, III, and IV), received distilled water and sodium arsenite (aqueous solution of 1.0, 1.5, and 2.0 mg/kg body weight, respectively) by intraperitoneal (i.p.) route. On postnatal day (PND) 12, the animals were sacrificed and brain tissue obtained. Paraffin sections (8 μm thick) stained with Cresyl Violet (CV) were observed for morphological and morphometric parameters. Arsenic induced programmed cell death (apoptosis) was studied using Terminal deoxyribonucleotidyl transferase mediated dUTP biotin Nick End Labeling (TUNEL) technique on the paraffin sections. Microscopy revealed decreased number and isolation of pyramidal neurons in superficial layers, misalignments of pyramidal cells in stratum pyramidale (SP) of CA1 and CA3 in experimental group III and IV, and presence of polymorphic cells in subgranular zone of ectal limb of dentate gyrus (suggestive of arsenic induced proliferation and migration of granule cells in the dentate gyrus). Morphometric assessments quantified and confirmed the microscopic findings. The mean nuclear area of pyramidal cells was increased and cell density was decreased in the CA1, CA3, and DG of experimental groups in comparison to the control group. Increase in the TUNEL positive cells in DG was observed in the experimental group IV, suggestive of increased apoptosis. These observations confirm vulnerability of pyramidal (CA1, CA3) and granule cells (DG) of hippocampus during RBGP.

Keywords

Apoptosis, arsenic, dentate gyrus, granule cells, hippocampus, morphometry, pyramidal cells

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Parul Kaushal ¹, Pushpa Dhar ¹, Somesh Meludurga Shivaprasad ², Raj D. Mehra ¹

Affiliations
1 Department of Anatomy, All India Institute of Medical Sciences, Ansari Nagar, New Delhi- 110029, IN
2 Department of Anatomy, Srinivas Institute of Medical Science and Research Centre, Mukka, Manglore-574146, IN

Abstract

Objective: The present study was undertaken to investigate the effects of early postnatal exposure to sodium arsenite (NaAsO₂) on rat testis. Materials and Methods: Wistar rat pups were administered aqueous solution of NaAsO₂, 1.5 mg/kg body weight (bw) (experimental) and distilled water (control), respectively, by intraperitoneal route (i.p.) from postnatal day (PND) 1 to 14. Testes were collected after 1, 7 and 36 days (at PND 15, 21 and 50) after the treatment period (PND1-14) from the animals and immersion fixed in Bouin’s fluid followed by paraffin embedding. Seven micrometer thick serial sections were cut and stained with hematoxylin and eosin for light microscopic observations. At PND 50, morphological features of sperms and their counting was carried out besides processing the perfusion-fixed testes for electron microscopy (EM). Results and Conclusions: The observations revealed an altered morphology of the seminiferous tubules (ST) along with degeneration and dissociation of spermatogenic cells in the experimental animals at PND 15, 21 and 50. Also, increased number of sperms with abnormal morphology and decreased sperm count was noted in the experimental animals. These features together with electron microscopic observations of abnormal mitochondria and apoptotic nuclei of spermatogonia and spermatocytes could be indicative of long-lasting adverse effects on the rat testis induced by exposure to As during early postnatal period.

Keywords

Arsenic, Postnatal period, Seminiferous tubules, sodium arsenite, spermatozoa, testis

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