Salt Deficient Diet Effects on Rat Adrenal Zona Glomerulosa Gene Expression

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: MON 723-757-Renin-Angiotensin-Aldosterone System/Endocrine Hypertension
Bench to Bedside
Monday, June 17, 2013: 1:45 PM-3:45 PM
Expo Halls ABC (Moscone Center)

Poster Board MON-752
Koshiro Nishimoto*1, Ruth B.S. Harris2, William E Rainey1 and Tsugio Seki2
1University of Michigan, MI, 2Georgia Regents University, Augusta, GA
Background: Aldosterone, which is under the control of the renin-angiotensin system (RAS), is the primary adrenocortical hormone regulating water and salt retention. A low salt diet activates the RAS and aldosterone production through an expansion of the adrenal zona glomerulosa (zG) 1. However, the RAS effects on zG gene expression have not been fully elucidated. In the current study, we hypothesized that activation of the RAS using a salt deficient diet (SDef) alters the transcriptome in zG. Hence, in this report, we took an unbiased approach to define the complete list of zG transcripts involved in RAS activation.

Methods: Adrenal glands and blood were collected from 11-week old Sprague-Dawley rats fed with either normal salt diet (NS) or SDef for 3 days. Blood was used for measurement of serum aldosterone. Adrenal glands were used for immunohistochemistry and laser-capture microdissection. Laser-captured samples were used for microarray analysis (Affimetrix).

Results: Serum aldosterone was much higher in SDef (792.4 ± 503.7 pg/mL) than in NS (55.3 ± 41.3 pg/mL, p<0.01). Immunohistochemistry showed that both NS and SDef rats had aldosterone synthase (CYP11B2, essential for aldosterone production) positive cell layers beneath the adrenal capsule. Therefore, we laser-captured an enriched population of CYP11B2-positive cells from the zG of both NS and SDef rats, as described previously 2. Although not statistically significant, microarray showed an enrichment of Cyp11b2 mRNA in SDef zG compared to NS zG (1.4x). In addition, the microarray analysis indicated that 79 transcripts were up-regulated in SDef. Interestingly, most of the up-regulated transcripts were involved in cell cycle regulation and/or proliferation. The 5 transcripts with the greatest up-regulation were cyclin-dependent kinase inhibitor 3 (11.6x); ribonucleotide reductase M2 (7.2x); topoisomerase (DNA) II alpha (6.1x); proline rich 11 (6.0x); and TPX2, microtubule-associated, homolog (5.8x).

Summary and Conclusions: We defined the zG transcripts involved in RAS activation of aldosterone synthesis following 3 days of SDef. Most activated genes were associated with cell proliferation. These transcripts may have important roles in zG expansion.

1. Mitani F, Suzuki H, Hata J, Ogishima T, Shimada H, Ishimura Y. A novel cell layer without corticosteroid-synthesizing enzymes in rat adrenal cortex: histochemical detection and possible physiological role. Endocrinology 135:431-438, 1994. 2. Nishimoto K, Rigsby CS, Wang T, Mukai K, Gomez-Sanchez CE, Rainey WE, Seki T. Transcriptome analysis reveals differentially expressed transcripts in rat adrenal zona glomerulosa and zona fasciculata. Endocrinology 153:1755-1763, 2012.

Nothing to Disclose: KN, RBSH, WER, TS

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Sources of Research Support: This work was supported by Grant DK43140 from the National Institute of Diabetes and Digestive and Kidney Diseases (to T.S. and W.E.R.) and by fellowships from the Federation of National Public Service Personnel Mutual Aid Associations and the Tachikawa Hospital, Tokyo, Japan (to K.N.).