Endocrine Abstracts

Aldosterone and glucocorticoids stimulate sodium transport by the renal tubule, which is important for blood pressure homeostasis. Corticosteroid excess and/or abnormal steroid hormone activity within the kidney can cause hypertension. Circulatory and urinary steroid concentrations can be measured routinely but steroid concentrations at a tissue and cellular level are largely unknown, and the kidney remains a “black box”. Mass spectrometry imaging (MSI) permits localisation of steroids in histological zones based on regional markers. This approach has been previously applied to localise steroids in brain and testes. Our aim was to use MSI to map and quantify glucocorticoids and aldosterone in different histological zones (cortex, medulla) of mouse kidney. Cryosections kidney from male C57BL6 mouse (age 12 weeks, n = 6) were subject to MSI analysis following Girard T reagent derivatisation and α-cyano-4-hydroxycinnamic acid matrix application. Matrix assisted laser desorption/ionisation (MALDI) was used as a sampling method, coupled to Fourier Transform Ion cyclotron mass spectrometry. Ions with m/z 458.3010 (Δppm = 0.65), 460.3166 (Δ ppm = 0.65), and 474.2957 (Δppm=1.05) were detected, using MALDI,in renal sections for derivatives of 11-dehydrocorticosterone, corticosterone and aldosterone respectively. Untargeted evaluation of ions was conducted to find regional markers that would allow definition of kidney histological zones. Heat maps indicated that corticosterone intensity was higher in the inner cortex than the rest of the kidney. In contrast 11-dehydrocorticosterone was detected in medulla and aldosterone signal was equally strong in medulla and outer cortex. Steroid co-localisation with zonal markers by MSI permitted mapping in functional renal zones. This approach provides fundamental new insights into the physiological control of sodium transport by steroids and opens doors to understanding changes in disorders of blood pressure.