These are the the references I found
1) In Walsh's Surviving Prostate Cancer book, 2nd Ed, he says on page 146 that "Sexual activity can elevate PSA as well:PSA levels can increase as much as 41 percent in less than an hour after ejaculation." Unfortunately, there is no reference. They mention that DREs can raise PSA. They do mention 2 studies that rule out bike riding as a cause of artificially elevated PSAs. No references on the bike studies or the DRE.
2) There was study was in Urology. 1997 Aug;50(2):239-43, that "When normal biologic variation was accounted for, 40% of men, at 24 hours after ejaculation, had total PSA levels above the baseline level. Similarly, 24 hours after ejaculation, the percent free PSA remained above baseline level in 10% and below baseline level in 35% of the men. " (Everybody had PSA below 4 at the start of the test.
The abstract is here http://www.ncbi.nlm.nih.gov/sites/en...RVAbstractPlus
3) This is a note about one patient., Hell J Nucl Med. 2007 May-Aug;10(2):119. A 52 year old man had a PSA of 1.2. His PSA was 6 and 7 on 2 separate occasions after having sex within 24 hours.
Here's the link http://www.ncbi.nlm.nih.gov/sites/en...RVAbstractPlus
So it looks like some males can have elevated PSAs from sex