{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,27]],"date-time":"2025-10-27T05:01:29Z","timestamp":1761541289273},"reference-count":52,"publisher":"Rockefeller University Press","issue":"3","content-domain":{"domain":["rupress.org"],"crossmark-restriction":true},"short-container-title":[],"published-print":{"date-parts":[[2016,3,1]]},"abstract":"<jats:p>Cytosolic Ca2+ buffers bind to a large fraction of Ca2+ as it enters a cell, shaping Ca2+ signals both spatially and temporally. In this way, cytosolic Ca2+ buffers regulate excitation-secretion coupling and short-term plasticity of release. The posterior pituitary is composed of peptidergic nerve terminals, which release oxytocin and vasopressin in response to Ca2+ entry. Secretion of these hormones exhibits a complex dependence on the frequency and pattern of electrical activity, and the role of cytosolic Ca2+ buffers in controlling pituitary Ca2+ signaling is poorly understood. Here, cytosolic Ca2+ buffers were studied with two-photon imaging in patch-clamped nerve terminals of the rat posterior pituitary. Fluorescence of the Ca2+ indicator fluo-8 revealed stepwise increases in free Ca2+ after a series of brief depolarizing pulses in rapid succession. These Ca2+ increments grew larger as free Ca2+ rose to saturate the cytosolic buffers and reduce the availability of Ca2+ binding sites. These titration data revealed two endogenous buffers. All nerve terminals contained a buffer with a Kd of 1.5\u20134.7 \u00b5M, and approximately half contained an additional higher-affinity buffer with a Kd of 340 nM. Western blots identified calretinin and calbindin D28K in the posterior pituitary, and their in vitro binding properties correspond well with our fluorometric analysis. The high-affinity buffer washed out, but at a rate much slower than expected from diffusion; washout of the low-affinity buffer could not be detected. This work has revealed the functional impact of cytosolic Ca2+ buffers in situ in nerve terminals at a new level of detail. The saturation of these cytosolic buffers will amplify Ca2+ signals and may contribute to use-dependent facilitation of release. A difference in the buffer compositions of oxytocin and vasopressin nerve terminals could contribute to the differences in release plasticity of these two hormones.<\/jats:p>","DOI":"10.1085\/jgp.201511525","type":"journal-article","created":{"date-parts":[[2016,2,16]],"date-time":"2016-02-16T03:04:13Z","timestamp":1455591853000},"page":"243-254","update-policy":"http:\/\/dx.doi.org\/10.1085\/jgp.crossmarkpolicy","source":"Crossref","is-referenced-by-count":7,"title":["Multiple cytosolic calcium buffers in posterior pituitary nerve terminals"],"prefix":"10.1085","volume":"147","author":[{"given":"Shane M.","family":"McMahon","sequence":"first","affiliation":[{"name":"Biophysics PhD Program 1 , 2 , and 3"},{"name":"Department of Neuroscience 1 , 2 , and 3"},{"name":"Physiology PhD Program, University of Wisconsin, Madison, WI 53705 1 , 2 , and 3"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Che-Wei","family":"Chang","sequence":"additional","affiliation":[{"name":"Biophysics PhD Program 1 , 2 , and 3"},{"name":"Department of Neuroscience 1 , 2 , and 3"},{"name":"Physiology PhD Program, University of Wisconsin, Madison, WI 53705 1 , 2 , and 3"},{"name":"Biophysics PhD Program 1 , 2 , and 3"},{"name":"Department of Neuroscience 1 , 2 , and 3"},{"name":"Physiology PhD Program, University of Wisconsin, Madison, WI 53705 1 , 2 , and 3"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Meyer B.","family":"Jackson","sequence":"additional","affiliation":[{"name":"Biophysics PhD Program 1 , 2 , and 3"},{"name":"Department of Neuroscience 1 , 2 , and 3"},{"name":"Physiology PhD Program, University of Wisconsin, Madison, WI 53705 1 , 2 , and 3"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"291","published-online":{"date-parts":[[2016,2,15]]},"reference":[{"key":"2023072623475191400_bib1","doi-asserted-by":"publisher","first-page":"378","DOI":"10.1016\/j.cellsig.2011.09.028","article-title":"The renaissance of Ca2+-binding proteins in the nervous system: secretagogin takes center stage","volume":"24","author":"Alp\u00e1r","year":"2012","journal-title":"Cell. 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